Lack of age-associated immune dysfunction in mucosal-associated lymph nodes

The magnitude of the immune response in old and young mice to trinitrophenylated bovine gamma-globulin was measured in various lymphatic sites at a cellular level using the plaque-forming cell assay. As we have previously shown, the number of splenic IgM, IgG, and IgA anti-TNP PFC progressively declined in aging C57BL/6J male mice. In addition, mice receiving antigen in the 4 footpads and the base of the tail exhibited similar decline in the number of PFC in the draining peripheral lymph nodes with increasing age. In contrast, mesenteric and mediastinal lymph node IgM, IgG, and IgA anti-TNP PFC response to TNP-BGG in complete Freund's adjuvant, i.p. or via gastric intubation, in old mice remained unimpaired compared with the number in younger mice. The data support the view that the mucosal-associated lymphoid system differs from the systemic system with regard to immune competence with age. Furthermore, the findings imply a site preference for a decline in immune function with aging.     

Evidence for histamine-induced auto-anti-idiotypic antibody immunoregulation in vivo

The in vivo effects of histamine injection in LAF₁ male mice on the immune reactivity to trinitrophenylated bovine γ-globulin was studied using plaque-forming cell (PFC) responses and their avidity distributions. Splenic anti-trinitrophenyl (anti-TNP) PFC responses of mice treated with histamine (5 × 10^?6 mol or 1 mg, intravenously) were significantly reduced in number and restricted in heterogeneity and characterized by a preferential loss of high-avidity IgG PFCs. The reduced PFC response in histamine-treated mice was dose and time dependent. No evidence of suppressor cell activity in the spleens from histamine-treated mice was demonstrable. Only histamine-treated mice produced a significantly high percentage of anti-idiotype-blocked, hapten-augmentable IgG PFCs, suggesting the presence of auto-anti-idiotypic activity. Immune sera taken from histamine-treated mice caused an inhibition of anti-TNP PFC in vitro. This PFC-inhibiting factor in immune sera of histamine-treated mice was an antibody of the IgG₁ and IgG_2a class, lacked anti-TNP antibody activity, but reacted with anti-TNP antibody of LAF₁ origin. Passive hemagglutination study of this sera showed anti-(anti-TNP F(ab′)₂-IgG) titer. Thus, the results of this study suggest that histamine in combination with antigen induces auto-anti-idiotypic antibody which, in turn, is involved in the normal regulation of the immune response to trinitrophenylated bovine γ-globulin in vivo.     

Selective suppression by auto-anti-idiotypic antibody of B-cell idiotype repertoires generated after stimulation with the same hapten on T-dependent and T-independent carriers

In the present study, we investigated whether auto-anti-idiotypic antibody in the immune sera from old mice could recognize antitrinitrophenyl (TNP) plaque-forming cells (PFC) generated after stimulation with the T-dependent and T-independent forms of the hapten, TNP. Young and old C57BL/6J male mice were immunized with a variety of T-dependent (TNP-bovine gamma-globulin, TNP-BGG; TNP-keyhole Limpet hemocyanin, TNP-KLH; ovalbumin, OVA; bovine serum albumin, BSA; BGG) and T-independent (TNP-Brucella abortus, TNP-BA; TBP-Ficoll; TNP-polyacrylamide beads, TNP-PAA) antigens either in complete Freund's adjuvant (CFA) or in soluble form. Splenic anti-TNP or antiprotein PFC responses were assayed for anti-idiotype-blocked, hapten- or protein-augmentable IgM, IgG and IgA PFC, 1-2 weeks after immunization. It was found that 8-month-old mice produced significantly a higher percentage of hapten augmentable (26-42%) IgM PFC response to T-independent antigens as compared with the 2-month-old mice (3-6% augmentation). Similarly, old mice produced a significantly higher percentage of hapten or protein augmentable (25-129%) IgG PFC response to T-dependent antigens as compared with the 2-month-old group (2-6% augmentation). The data support the view that age-related regulation of auto-anti-idiotypic antibody is a general phenomenon for immune responses to T-dependent and T-independent antigens. Hapten-reversible inhibition of plaque formation was used to determine whether anti-idiotypic antibody containing antisera from old mice could inhibit B-cell idiotype repertoires generated after stimulation with the same hapten, TNP, on T-dependent and T-independent carriers. Pools of immune sera from 8-month-old mice primed with T-dependent TNP-BGG or TNP-KLH antigens but not with T-independent TNP-PAA or TNP-BA antigens, or with the proteins OVA, BSA, or BGG selectively inhibited IgM, IgG, and IgA anti-TNP PFC from 2-month-old mice that were previously primed with either TNP-BGG or TNP-KLH. In contrast, immune sera from old mice primed with TNP on either T-dependent or T-independent carriers inhibited anti-TNP PFC from mice primed with T-independent TNP-PAA or TNP-BA antigens. Immune sera from old mice primed with OVA or BSA only inhibited the respective antiprotein PFC. The immune sera from young mice did not show any appreciable inhibition of PFC generated after stimulation by any of the antigens studied.(ABSTRACT TRUNCATED AT 400 WORDS)     

Strain differences in the development of auto-anti-idiotypic antibody regulation with age: genetic linkage to the Igh-C locus

The effect of age on the appearance of anti-idiotype (Id)-blocked, hapten-augmentable plaque-forming cells (PFC) in various strains of mice was investigated. Strains of mice at 2 and 6-11 months of age were immunized with 500 micrograms trinitrophenylated bovine gamma-globulin (TNP-BGG) in complete Freund's adjuvant (CFA) intraperitoneally. Splenic IgM and IgG anti-TNP PFC responses were assayed for anti-Id-blocked, hapten-augmentable PFC 14 days after immunization. It was found that strains differ with regard to the age at which they produce anti-Id-blocked, hapten-augmentable PFC. C57BL/6J (B6), DBA/1J, and C3H/HeJ mice produced a significantly high percentage of hapten-augmentable IgG anti-TNP PFC at 8-9 months of age as compared with the 2-month-old group. In contrast, 129/J, AKR/J, and C57L/J mice produced a significantly low percentage of hapten-augmentable PFC at 6-7 months of age as compared with the 2-month-old group. The CBA/J mice were high-hapten-augmentable plaque producers at both 2 and 7 months of age. SJL/J mice were, on the other hand, low producers at 2 and 11 months of age. Immune sera from high hapten-augmentable plaque-producing strains caused a hapten-reversible block of plaque formation by spleen cells from TNP-BGG-immune C57BL/6J mice and also revealed anti-(anti-TNP F(ab')2-IgG) titer as assayed by passive hemagglutination. This PFC-inhibiting activity in the immune sera of old C57BL/6J mice was an antibody of the IgG2a and IgG3 classes, lacked anti-TNP antibody activity, but reacted with anti-TNP antibody of C57BL/6J origin. Genetic analysis between high hapten-augmentable plaque production and allotypes in the (129/J X B6) crosses of the same H-2b haplotypes revealed that all of the backcrosses and F2 with high hapten-augmentable plaque production had the Igh-1a allele of the high-producer, 129/J mouse. In contrast, the crosses with low hapten-augmentable plaque production were homozygous for the Igh-1b allele of the low-producer, B6 mouse. The data suggest strain differences in the development of auto-anti-idiotypic antibody regulation with age which may be controlled by a gene(s) linked to the Igh-C locus.     

Production of auto-anti-idiotypic antibody during the normal immune response. XII. Enhanced auto-anti-idiotypic antibody production as a mechanism for apparent B-cell tolerance in rabbits after feeding antigen

Rabbits fed trinitrophenylated bovine serum albumin (TNP-BSA) generated fewer anti-TNP plaque-forming cells but greater numbers of hapten (TNP)-augmentable IgM and IgG PFC following immunization with TNP-Ficoll or TNP-Brucella abortus than did animals not previously fed antigen. Spleen and mesenteric and bronchial lymph nodes were similarly affected. In addition more auto-anti-idiotype (Id) antibody (anti-anti-TNP) was eluted by hapten from spleen cells of antigen-fed rabbits than from spleen cells of control rabbits not prefed antigen. Gel filtration studies ruled out the possibility that the Id binding activity in the eluates was due to immune complexes. The isotype of the anti-Id was IgG except in one rabbit where it was IgM. The results are consistent with the interpretation that the production of auto-anti-Id antibody is one of the factors responsible for the specific depression of the IgM and IgG immune responses which follows antigen feeding. In contrast the antigen feeding resulted in priming for an IgA anti-TNP response without detectable hapten-augmentable IgA PFC.     

Enhancement of antigen-induced interleukin 4 and IgE production by specific IgG1 in murine lymphocytes.

Conalbumin (CA)-specific type 2 helper T cell (Th2) clone, D10G4.1 (D10) produces IL4 when stimulated with varying doses of TNP-CA in the presence of mitomycin C-treated C3H spleen cells or purified B cells as antigen-presenting cells (APC). The production of IL4 was assessed by bioassay and by expression of IL4 mRNA. IL4 production reached maximum at 100 micrograms/ml of TNP-CA, whereas 1 microgram/ml of the antigen induced less than 10% of the maximum level of IL4. This lower level of IL4 production was augmented to the maximum level when monoclonal anti-TNP IgG1 was added to the culture at 0.5-1 microgram/ml. Anti-TNP IgE, but not anti-TNP IgM, was also effective, though IgE was 1/10 as effective as IgG1. IgG1 with an irrelevant specificity and F(ab')2 of anti-TNP IgG1 did not show augmenting effects. Moreover, the enhancement by anti-TNP IgG1 was completely abolished by monoclonal antibody against murine Fc gamma RII, 2.4G2. These results suggest that a low dose of the antigen complexed with IgG1 is focused on APC by means of Fc gamma RII, processed, and presented efficiently to the Th2 clone. On the other hand, the co-culture of D10 with normal C3H B cells in the presence of 1-100 micrograms/ml TNP-CA resulted in polyclonal IgE production. Anti-TNP IgG1 markedly augmented the lower level of IgE production induced by a suboptimal dose of the antigen (1 microgram/ml). This augmentation was shown to be dependent on endogenous IL4 because the enhancement was abolished by monoclonal anti-IL4 (11B11).     

Characterization and genetic control of the immune response to synthetic polypeptide antigens of defined geometry.

Both humoral and cell-mediated immune responses to the synthetic helical hapten-carrier conjugate poly-Glu-Tyr-Lys(TNP)-(Glu-Tyr-Ala)5 were found to be linked to the major histocompatibility locus in mice and guinea pigs. The responder mouse strains (H-2d haplotype) showed a primary IgM response with an IgG component appearing after the secondary immunization. The antibody response was accompanied by a positive DTH reaction in responder strains. Nonresponder mice (H-2b or H-2k haplotypes) showed neither IgM nor IgG antibodies and the DTH reaction was negative. Administration of the antigen as a complex with an immunogenic carrier was not effective in inducing a response in nonresponder mice. In guinea pig studies, it was found that strain 2 animals were able to mount an antibody response against the TNP-hapten and a DTH response against the polypeptide backbone. Strain 13 animals gave no anti-TNP antibodies at the lower dose levels and DTH activity was entirely negative for all doses of immunizing antigen. Replacement of the TNP hapten by the arsanilazo dipeptide derivative, BOC-gly-ARA-tyrosine, converted the nonresponder strain 13 guinea pigs into complete responders showing antibody and DTH reactions to both the hapten and the polypeptide backbone.     

Induction of antigen-specific antibody responses in primed and unprimed B cells. Functional heterogeneity among Th1 and Th2 T cell clones

CD4+ T cells have been recently divided into two subsets. The functions of these subsets are thought to be distinct: one subset (Th1) is responsible for delayed type hypersensitivity responses and another (Th2) is primarily responsible for induction of antibody synthesis. To more precisely define the roles of both subsets in humoral immune responses, we examined the ability of a panel of nominal antigen specific Th1 and Th2 clones to induce anti-TNP specific antibody synthesis in TNP-primed or unprimed B cells. Four of nine Th1 clones induced little or no antibody synthesis with TNP-primed B cells. However, five other Th1 clones were very effective at inducing IgG anti-TNP plaque-forming cell (PFC) responses in primed B cells. One of these Th1 clones was analysed in detail and found to also provide helper function for unprimed B cells. Cognate B-T cell interaction was required for induction of both primary and secondary responses with this clone, indicating that a Th1 clone could function as a "classical" Th cell. The seven IL-4 producing Th2 clones examined were also heterogeneous in their ability to induce antibody secretion by TNP-primed B cells. Although four of the Th2 clones induced IgG and IgM anti-TNP PFC responses, two Th2 clones induced only IgM and no IgG antibody, and another clone failed to induce any anti-TNP PFC. All Th2 clones failed to induce any anti-TNP PFC. All Th2 clones produced high levels of IL-4, but "helper" Th2 clones produced significantly greater amounts of IL-5 than "non-helper" Th2 clones. These studies indicate that some IL-2- and some IL-4-producing T cell clones can induce TNP-specific antibody in cell clones can induce TNP-specific antibody in primed and unprimed B cells, and that Th1 and Th2 clones are heterogeneous in their ability to induce Ig synthesis. Therefore, although T cell clones can be classified as Th1 or Th2 types according to patterns of IL-2, IFN-gamma, or IL-4 synthesis, the functional capacity to induce antibody synthesis cannot be predicted solely by their ability to secrete these lymphokines.     

Taenia crassiceps: Serum and surface immunoglobulins in metacestode infections of mice

Serum levels of IgM, IgA, IgG1, IgG2a, IgG2b, and IgG3 were measured weekly for 8 weeks by radial immunodiffusion in pooled sera from female BALB/c and BDF1 mice with primary and secondary Taenia crassiceps infections and age-matched normal control mice of each strain. Although increases in levels of all immunoglobulin classes occurred during primary and secondary infections in both strains of mice, the only consistent changes common to both strains of mice were higher levels of IgG1 and IgG3 in early weeks of secondary infections as compared to primary infections, and high levels of IgG1 late in primary infections. High levels of IgG3 occurred late in primary infections in BDF1 mice but not in BALB/c mice. It was not possible to correlate increased levels of any one immunoglobulin class either with cytotoxic activity of early immune serum or with the onset of the cellular encapsulation response in secondary infections. IgM, IgA, IgG1, IgG2a, IgG2b, and IgG3 could be demonstrated on the surface of washed fixed larvae from long-term infected donor mice by the indirect fluorescent antibody method. Living T. crassiceps larvae were capable of shedding fluorescent label within 1 hr at room temperature, but not at 4 C after staining with either rabbit anti-T. crassiceps serum or rabbit anti-mouse immunoglobulin serum and fluorescein-conjugated goat anti-rabbit globulin.     

Immunization with extracellular vesicles excreted by Toxoplasma gondii confers protection in murine infection,activating cellular and humoral responses

The study aim was to analyze whether microvesicles and exosomes, named extracellular vesicles (EVs), purified from Toxoplasma gondii are able to stimulate the protective immunity of experimental mice when administered, as challenge, a highly virulent strain. EVs excreted from T. gondii tachyzoites (RH strain) were purified by chromatography and used for immunization assays in inbred mouse groups (EV-IM). Chronic infected (CHR) and naive (NI) mice were used as control groups, since the immune response is well known. After immunizations, experimental groups were challenged with 100 tachyzoites. Next, parasitemias were determined by real-time PCR (qPCR), and survival levels were evaluated daily. The humoral response was analyzed by detection of IgM, IgG, IgG1 and IgG2a, and opsonization experiments. The cellular response was evaluated in situ by immunohistochemistry on IFN-γ, IL-10, TNF-α and IL-17 expression in cells of five organs (brain, heart, liver, spleen and skeletal muscles). EV immunization reduced parasitemia and increased the survival index in two mouse lineages (A/Sn and BALB/c) infected with a lethal T. gondii strain. EV-IM mice had higher IgG1 levels than IgM or IgG2a. IgGs purified from sera of EV-IM mice were able to opsonize tachyzoites (RH strain), and mice that received these parasites had lower parasitemias, and mortality was delayed 48 h, compared with the same results from those receiving parasites opsonized with IgG purified from NI mice. Brain and spleen cells from EV-IM mice more highly expressed IFN-γ, IL-10 and TNF-α. In conclusion, EV-immunization was capable of inducing immune protection, eliciting high production of IgG1, IFN-γ, IL-10 and TNF-α.     

Echinococcus multilocularis: Immunoglobulin and antibody response in C57BL6J mice

Each of 50 male C57BL/6J mice was infected intraperitoneally with 50 cysts of Echinococcus multilocularis. At 2, 4, 6, 8, and 14 weeks after infection, 10 mice were sacrificed, their larval cyst masses weighed, and their sera collected. Each serum sample from uninfected control and infected mice was adsorbed twice with two batches of E. multilocularis antigen conjugated to Sepharose beads. The concentrations of IgG1, IgG2a, IgG2b, IgM, and IgA in unadsorbed and IgG1, IgG2b, and IgM in adsorbed sera were quantified by the radial immunodiffusion technique. Hydatid mice produced increasingly large amounts of IgG1 and IgM; small measurable increases of IgG2b and no significant increases of IgG2a and IgA were observed during the course of infection. During the rapid growth phase of the cysts (6 to 14 weeks) IgG1 antibodies were found to range from 86 to 93% and IgM antibodies from 17 to 33% of the total IgG1 and IgM. However, the actual protein concentrations of IgM antibodies (761 and 1215 mg/dl) were higher than the sum of the protein concentrations of IgG1 and IgG2b antibodies (411 and 779 mg/dl). The significance of the relative concentrations of IgM, IgG1, IgG2a, and IgG2b antibodies is discussed with reference to their effectiveness in antibody-dependent cellular cytotoxicity and complement-mediated lysis in the control of alveolar hydatid disease.     

In vivo immune response to TNP hapten coupled to thymus-independent carrier lipopolysaccharide

Lipopolysaccharide has been utilized as a carrier for the TNP hapten, producing an antigen which induces an in vivo thymus-independent antibody response to TNP as determined using athymic nude mice and their normal littermates. The immune response to TNP-LPS was investigated at both the antibody-forming cell and the serum antibody levels.The primary response to an optimal dose of TNP-LPS (1.0 μg) exhibited unusual kinetics reaching a sharp peak on day 3 of 58,000 anti-TNP PFC/spleen. Serum antibody to TNP was first detected on day 3 and reached a maximum log₂ titer of 17.5 on day 5, an uncommonly high level for hapten-carrier conjugates and most carriers. Both the anti-TNP serum antibody and PFCs were exclusively IgM. No IgG antibody was detected in the primary response through 28 days postimmunization, nor was any detected in any experiment described in this paper. The primary PFC response to 1.0 μg of TNP-LPS was specific for TNP, producing no evidence of polyclonal antibody synthesis. The relative affinities of PFC-secreted antibody were investigated using hapten inhibition. The hapten inhibition curves for TNP-LPS and TNP-SRBC were very similar, indicating that relatively high affinity antibody was elicited by TNP-LPS. The secondary response to this dose following priming with TNP-SRBC or TNP-LPS was similar to the primary response, though the peak was less sharp in both cases. The response to the homologous secondary challenge shifted somewhat, reaching a peak on days 3–4. The effect of various doses in priming or challenging for the secondary response to TNP-LPS was investigated. Using an increased PFC response as a criterion, no dose was optimal for priming or immunological memory to TNP-LPS. While the adoptive primary response to TNP-LPS reached a low level peak on day 7, the adoptive secondary attained a maximum on day 6. This shift in kinetics in intact mice and in adoptive hosts in comparing primary to secondary responses indicated that a state of B cell priming may be induced. However, its full expression may be suppressed by endogenous factors at the time of priming, such as the high level of circulating anti-TNP antibody or residual antigen. Adoptive transfer would remove the cells from these influences, allowing such B cell priming to manifest itself fully.     

The asymmetry in idiotype-isotype expression in the response to phosphocholine is due to divergence in the expressed repertoires of Lyb-5+ and Lyb-5- B cells

The X-linked CBA/N immune defect was used to investigate the roles of Lyb-5- and Lyb-5+ B cells in the memory response to PC-KLH (phosphocholine-conjugated keyhole limpet hemocyanin). (CBA/N X BALB/c)F1 (CB) male mice express the xid mutation and thereby lack the Lyb-5+ B cell subset, whereas their female littermates are normal and express both Lyb-5+ and Lyb-5- B cells. After priming with PC-conjugated hemocyanin (PC-Hy) in complete Freund's adjuvant, female B cells produce three phenotypic sets of PC-KLH-specific antibody. The first set (group I) is dominated by T15+, IgM, IgA, and IgG3, PC-specific antibodies. The second subset (group II) is specific for phenylphosphocholine (PPC), and is dominated by T15-, IgG1, and IgG2 antibodies. The third set (group III) recognizes an epitope(s) composed of both the PPC hapten and carrier determinants. PC-Hy-primed B cells from immune defective CB male mice produce the same number of IgG1 and IgG2 plaque-forming cells (PFC) as do PC-Hy-primed normal female cells, and these PFC are also predominantly T15- and PPC specific (group II). In addition, a significant amount of group III IgG1 and IgG2 antibody is observed in the immune defective male response. In contrast to female B cells, immune defective male B cells produce a low IgM, IgA, and IgG3 memory response that is not composed of PC-specific (group I) antibodies; in fact, most of these antibodies arise from group III precursors and are not inhibited by either PC or PPC. PC-specific antibodies usually represent less than 25% of the anti-PC-KLH response in immune defective mice; however, these PC-specific antibodies are predominantly T15-. These data suggest that the Lyb-5-B cells in both normal and immune defective mice produce the T15-, IgG1, and IgG2 antibodies that dominate the secondary immune response to PC-KLH, and that the Lyb-5+ B cells produce the T15+, IgM, IgA, and IgG3 portion of the secondary response in normal mice. This hypothesis was confirmed by priming normal mice with the R36a strain of Streptococcus pneumoniae or with PC-Hy in saline. These forms of PC-antigen prime only the Lyb-5+ B cell subset. The adoptive transfer of these two B cell sources results in an anti-PC-KLH response that is T15 dominant and totally PC inhibitable.(ABSTRACT TRUNCATED AT 400 WORDS)     

Defective resistance to Plasmodium yoelii in CBA/N mice.

The role of B lymphocytes in resistance to malaria was studied in defective and normal F1 mice derived from CBA/N mice, a strain with an X-linked B cell defect. When infected with normally nonlethal Plasmodium yoelii, immune defective F1 male mice had higher parasitemias and more prolonged infections than normal F1 mice, as well as a 50% mortality rate. Before infection the plasma levels of IgM and IgG were lower in defective F1 males than normal F1 mice. The polyclonal IgM and IgG responses of infected abnormal F1 mice were delayed and lower in absolute magnitude than those of normal F1 mice. Furthermore, specific IgM and IgG anti-plasmodial antibody titers, as determined by radioimmunoassay, were depressed on day 12 in the defective F1 males. Although IgG titers approached those of the normal F1 mice on day 19, defective F1 male IgM titers remained depressed. These data demonstrate that an X-linked gene that affects B cell function influences malarial resistance in mice, presumably via a decreased specific IgM response, and the slow development of a specific IgG response to P. yoelii infection.     

Cannabinoid Receptor 2 (CB2) Plays a Role in the Generation of Germinal Center and Memory B Cells,but Not in the Production of Antigen-Specific IgG and IgM,in Response to T-dependent Antigens

The cannabinoid receptor 2 (CB2) has been reported to modulate B cell functions including migration, proliferation and isotype class switching. Since these processes are required for the generation of the germinal center (GC) and antigen-specific plasma and memory cells following immunization with a T-dependent antigen, CB2 has the capacity to alter the quality and magnitude of T-dependent immune responses. To address this question, we immunized WT and CB2^−/− mice with the T-dependent antigen 4-hydroxy-3-nitrophenylacetyl (NP)-chicken-gamma-globulin (CGG) and measured GC B cell formation and the generation of antigen-specific B cells and serum immunoglobulin (Ig). While there was a significant reduction in the number of splenic GC B cells in CB2^−/− mice early in the response there was no detectable difference in the number of NP-specific IgM and IgG₁ plasma cells. There was also no difference in NP-specific IgM and class switched IgG₁ in the serum. In addition, we found no defect in the homing of plasma cells to the bone marrow (BM) and affinity maturation, although memory B cell cells in the spleen were reduced in CB2^−/− mice. CB2-deficient mice also generated similar levels of antigen-specific IgM and IgG in the serum as WT following immunization with sheep red blood cells (sRBC). This study demonstrates that although CB2 plays a role in promoting GC and memory B cell formation/maintenance in the spleen, it is dispensable on all immune cell types required for the generation of antigen-specific IgM and IgG in T-dependent immune responses.     

In vivo immune stimulation of mice by anti-μ antibodies: Generation of high serum levels of a low molecular weight IgM product

These studies show that anti-μ antibodies first injected into BALB/c mice as young adults exhibit a marked in vivo stimulatory effect, manifested by the appearance in circulation of large quantities of an aberrant IgM product. This stimulatory property extends to both rabbit and goat anti-μ antisera which have been raised against either myeloma or normal IgM but is not demonstrable for normal sera or antisera against γ or α heavy chains. The kinetics of appearance of this IgM product provide support for active generation upon stimulation, as opposed to immediate release of a preformed substance. Production of this form of IgM is accompanied by slight elevations in serum levels of IgG1 and normal IgM but unaltered levels of IgG2 and IgA. A molecular weight similar to that of IgG together with the demonstrated presence of light chains suggest that the aberrant product is likely a monomer of IgM. This stimulatory process appears to be thymus dependent because it cannot be induced in congenitally athymic (nude) mice unless they have been thymus reconstituted. Several test protocols involving adult-initiated anti-μ treatment resulted in immune responses to two thymus-dependent complex antigens (rabbit serum and sheep red blood cells) as well as generation of the aberrant IgM product in normal control mice but failed to render nude mice responsive to either antigen. It is thus apparent that although anti-μ antibodies can generate a stimulus in adult mice which results in production of an otherwise undetectable IgM product, the stimulus is not generally interpreted biologically as an immune “signal” complementary to antigen stimulation.     

Beta 2-adrenoceptor stimulation increases the number of antigen-specific precursor B lymphocytes that differentiate into IgM-secreting cells without affecting burst size.

Previous studies have shown that early addition of a beta 2-adrenergic agonist to whole splenocyte cultures immunized with SRBC induced an increase in the number of cells secreting Ag-specific antibody. Because of the low frequency of Ag-specific B lymphocytes in these cultures, it has been difficult to determine the cellular mechanism by which this increase is produced. To gain insight into this cellular mechanism, the present study was designed to evaluate the responsiveness of TNP-specific B lymphocytes cultured at both high density and limiting dilution with keyhole limpet hemocyanin (KLH)-specific, IL-4-producing Th lymphocytes, TNP-KLH, and the beta 2-adrenergic agonist, terbutaline. The results showed that a maximal twofold increase in both the number of anti-TNP IgM-secreting cells and the amount of anti-TNP IgM secretion occurred in terbutaline-exposed lymphocytes after 5 days of bulk culture. This response occurred in a concentration-dependent manner and was inhibited by concomitant culture with beta-adrenoceptor antagonists. No appreciable change was measured in the level of either IgG1 secretion in terbutaline plus Ag-exposed bulk cultures or MHC class II expression on terbutaline plus Ag-exposed TNP-specific B lymphocytes as compared with Ag alone. These data raised the possibility that beta 2-adrenoceptor stimulation induced either the differentiation of a larger proportion of TNP-specific B lymphocyte precursors into anti-TNP IgM-secreting cells, or the extensive proliferation of a constant number of TNP-specific B lymphocyte precursors, or both. Limiting dilution results showed that beta 2-adrenoceptor stimulation induced a twofold increase in the number of TNP-specific B lymphocyte precursors that differentiated into anti-TNP IgM-secreting cells, without affecting the number of anti-TNP IgM-secreting cells produced by each precursor clone.     

Selective improvement of thymus and some T cell dysfunctions in NZB mice by in utero thymulin treatment

NZB mice were treated during gestation with thymulin, a thymus-secreted, zinc-associated nonapeptide. Control pregnant NZB mice received either zinc alone or saline alone. Offspring from all three groups of NZB mothers, and age-matched DBA/2 mice, were tested for the following immunologic parameters: thymulin serum levels at 2 and 5 wk of age; splenic anti-sheep red blood cell (anti-SRBC) plaque-forming cell (PFC) numbers after immunization at birth or at 2 wk of age; anti-human gamma-globulin (anti-HGG) antibody titers after immunization at 2 wk of age, with or without prior tolerance induction at birth with deaggregated HGG; spontaneous IgM serum levels at 2 and 5 wk of age; spontaneous splenic anti-trinitrophenyl (anti-TNP) PFC numbers at 2 wk of age. As compared with DBA/2 mice, young NZB mice exhibited low circulating thymulin titers, high antibody responses to SRBC and to HGG, resistance to tolerance induction by deaggregated HGG, increased spontaneous IgM serum levels, and increased spontaneous anti-TNP PFC numbers. However, marked reductions in anti-SRBC and anti-HGG antibody production, both thymus-dependent responses, were observed in the young NZB offspring of thymulin-treated mothers as compared with NZB controls born from zinc- or saline-treated mothers. A delay in the postnatal decrease of serum thymulin levels was also noted in the offspring of thymulin-treated mothers. Interestingly, these effects of in utero thymulin treatment tended to become more pronounced with advancing age during the postnatal period. Conversely, IgM serum levels, spontaneous anti-TNP PFC and sensitivity to tolerance induction were not affected by thymulin treatment during fetal life. Taken together, the data suggest that in utero exposure to pharmacologic concentrations of thymulin induces a persistent and selective improvement of some thymus and T cell dysfunctions but has no effect on intrinsic B cell abnormalities of NZB mice.     

Characterization of Background Anti-Trinitrophenyl Plaque-Forming Cells Observed in Several Strains of Mice

Normal mice have a large number of background anti-trinitrophenyl (TNP) antibody-forming cells (AFC) in their spleens (about 40–50 anti-TNP PFC/10⁶ cells). We investigated this among several mouse strains, i.e., C57BL/6, C3H/He, Balb/c, ddd, and ICR mice, and found that all strains had a similar number of anti-TNP PFC (plaque-forming cells). Developmental aspects of background anti-TNP PFC in the ontogenic process were also investigated. The number of anti-TNP PFC increased logari thmically during the first few days of age, reached a peak on the 13th day and attained a constant value within 30 days. Neonatal thymectomy did not decrease the number of background anti-TNP PFC but such treatment decreased the anti-TNP PFC response to TNP-HRBC (horse red blood cells) immunization. Germ-free ICR mice had a number of background anti-TNP PFC similar to that of conventional ICR mice. Avidity of background anti-TNP PFC was compared among mice of several ages and it was shown that there were no differences among them. These results suggest that the occurrence of these background anti-TNP PFC is not elicited by the immune response but by the natural maturation of precursors of AFC without antigenic stimulation.