Inhibition of offspring response to HEL-CFA by administration of anti-HEL MAB to the mother is not related to the predominant idiotype, IdXE, or specificity of the MAB.

In the neonatal suckling mouse, the antibody response to HEL-CFA can be inhibited by administration of certain anti-HEL monoclonal antibodies to the mother. The murine primary response to hen egg-white lysozyme (HEL), which can be elicited in A/J mice as early as 7 days of age, is characterized by a predominant specificity that includes the 3 N-terminal amino acids of HEL (TIP-dependence) and by a predominant idiotype, IdXE. A panel of murine IgG1 anti-HEL mAbs was administered to the suckling offspring via the mother. These mAbs were not equivalent in their effects on the offspring. Only two of six IgG1 mAbs, 2F4/2E5 (IdXE-positive, TIP-dependent) and 2D1 (IdXE-negative, TIP-independent), consistently induced suppression of the response of A/J offspring when immunized at 16-20 days of age with HEL-CFA. Suppression averaged 71% for 2F4/2E5 and 74% for 2D1 and was always statistically significant (P less than .05) when 275 micrograms mAb was administered IP to the mother within 24 hr postpartum. Since 2D1 is IdXE-negative and TIP-independent, neither of these properties appears to be crucial for suppression. Differences in transfer of the mAbs from the mother to the offspring or differences in catabolism of the mAbs in the offspring were not detected. When various characteristics of the mAbs such as affinity, idiotypy, and fine specificity were considered, there was no single factor which determined suppression. One of the two mAbs that suppressed the offspring response, 2D1, is idiotypically highly connected in the anti-HEL mAb panel. This observation suggests that idiotypic interactions in the developing neonatal repertoire with subsequent perturbation of T and B cell repertoire development may be an area for future investigation.     

Specificity,avidity, and size of B-lymphocyte populations during ontogeny

The size and specificity of plaque-forming cell precursors (PFC) in murine fetal liver, neonatal, and adult spleen were studied in an adoptive transfer system. In this system, anti-4-hydroxy-3-iodo-5-nitrophenylacetic acid (anti-NIP) and anti-2,4,6-trinitrobenzene sulfonic acid (anti-TNP) direct PFC are generated from bone marrow-derived (B) cell precursors in fetal liver between 17 and 20 days of gestation and in 6- or 14-day neonatal spleen. PFC generated from fetal liver and neonatal and adult spleen cells are specific in that they lyse either NIP-coupled SRBC or TNP-coupled SRBC but not both. The generation of specific anti-NIP and anti-TNP PFC from precursors in fetal liver is primarily independent of antigenic stimulation. In contrast, the anti-NIP and anti-TNP responses generated from neonatal and adult spleen are antigen dependent. Both high-avidity PFC (detected with SRBC indicators coupled at low hapten density) and low-avidity PFC (detected with SRBC coupled at high hapten density) are generated from fetal liver and neonatal spleen cells; however, the proportion of high-avidity PFC precursors in adult spleen is at least threefold greater than in fetal liver or neonatal spleen. Analysis by velocity sedimentation indicates that most high-avidity PFC precursors are small lymphocytes in fetal liver, medium lymphocytes in 6-day neonatal spleen, and small lymphocytes in 14-day-old and adult spleen. Low-avidity PFC precursors are primarily medium-sized lymphocytes in fetal liver and 6-day neonatal spleen. In 14-day-old and adult spleen almost all high- and low-avidity PFC precursors are small lymphocytes. The results are discussed in terms of relative changes in the pool sizes of these lymphocyte populations.     

Murine bone marrow IgA responses to orally administered sheep erythrocytes

Specific immunization protocols have been established for the induction of murine bone marrow IgA responses to the T cell-dependent (TD) antigen sheep red blood cells (SRBC). Systemic immunization, either i.p. or i.v., followed by a second injection, induced splenic IgM and IgG responses and a bone marrow IgM response. No significant IgA responses were observed in either lymphoid tissue compartment. Oral immunization with SRBC by gastric intubation for 2 days, followed 1 wk later by an i.p. injection of SRBC resulted in a splenic IgA plaque-forming cell (PFC) response, but did not elicit a bone marrow IgA response. Repeated daily gastric intubation of SRBC to C3H/HeN and C3H/HeJ mice led to the previously reported pattern of systemic unresponsiveness in C3H/HeN mice and good anamnestic type IgM, IgG, and IgA splenic anti-SRBC PFC responses in the C3H/HeJ strain upon parenteral challenge. Oral administration of SRBC for 14 days to C3H/HeN mice, followed by systemic SRBC challenge, resulted in diminished splenic PFC responses of all isotypes, whereas gastric intubation of SRBC for 28 days led to complete systemic unresponsiveness to antigen in C3H/HeN mice. Interestingly, the repeated oral administration of SRBC resulted in significant bone marrow IgA PFC responses upon i.p. challenge in both C3H/HeN and C3H/HeJ mouse strains. The bone marrow IgA responses were clearly dependent upon chronic oral exposure to SRBC, because gastric intubation with SRBC for 2 consecutive days/wk for 10 wk also induced bone marrow and splenic IgA anti-SRBC PFC responses in C3H/HeN mice. These results suggest that memory B cells reside in the bone marrow of orally immunized mice and can yield anamnestic-type responses to challenge with the inducing antigen. The memory cells may arise in the Peyer's patches of the gut and migrate to the bone marrow. The possibility that the bone marrow is a component of the common mucosal immune system in mammals is suggested by this study.     

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.     

Mouse fetal liver cells manifest antigen-specific suppressor activity

Liver cells obtained from C57B1/6J mice at different stages of development suppress the primary in vitro induced immune response. Fetal liver cells showed the strongest suppression of the PFC response, an effect which was gradually lost after birth. Thymic or splenic cells were ineffective in suppressing the PFC response under conditions where fetal liver cells from the same donors were highly active. Liver cells from newborn C57B1/6J athymic nude mice were equally suppressive as cells from their normal thymus-bearing littermates. Preculture of liver cells from 18-day-old fetuses with antigen homologous to that used in the indicator system increased suppressor activity severalfold compared with other experimental groups in which cells have been precultured in medium alone or with the addition of a heterologous antigen. The data suggest that antigen-specific suppressor activity is present in fetal liver cells. The possible relevance of these findings in relation to acquisition of self-tolerance is discussed.     

Characterization of the immunodeficiency of RIIS/J [corrected] mice. I. Association with the CD5 (LY-1) [corrected] B cell lineage

RIIIS/J mice produce low antibody responses to several polysaccharide Ag of bacterial origin. They have low levels of serum IgM and IgG3 and high levels of serum IgG2a and IgG2b. Low serum IgM and IgG3 have been attributed to a low frequency of CD5 (Ly-1) B cells, which play an important role in the production of natural antibodies. Indeed, RIIIS/J mice have a low frequency of CD5 (Ly-1)+, IgM bright+, Ly-5 (B220)dull+ (i.e., CD5 (Ly-1) B) cells in their peritoneum. RIIIS/J mice treated with LPS produce a low anti-bromelain-treated mouse RBC splenic plaque-forming cell response and a normal anti-mouse transferrin splenic PFC response. Those data are compatible with the fact that CD5 (Ly-1) B cells contain the precursors of B lymphocytes secreting anti-bromelain-treated mouse RBC antibody. However, they have a higher frequency of IgM bright+, Mac-1+ cells in their peritoneum. These cells represent the CD5 (Ly-1) "sister population" of CD5 (Ly-1) B cells described by others. This suggests that characteristics usually associated with the CD5 (Ly-1) lineage are applicable only to the CD5 (Ly-1)+ Mac-1+ IgM+ population, but not the related CD5 (Ly-1)- Mac-1+ IgM+ population. RIIIS/J mice should thus prove a valuable model to study the CD5 (Ly-1) B cell lineage.     

Ontogeny of B cell precursors responding to alpha 1- greater than 3 dextran in BALB/c mice

The ontogeny of BALB/c B cell repertoire with specificity for alpha 1- greater than 3 dextran (DEX) was examined by using monoclonal anti-idiotype antibodies (MAID). Anti-DEX B cell precursors were absent from donor mice that were less than 5 days old. Precursors were first detected in mice from 5 to 11 days of age, but at a very low frequency of less than 1 in 10(8). In older mice, the frequency of anti-DEX precursors increased to approximately adult levels. Seventy-five percent of splenic foci from 5 to 11-day-old donors expressed IgA, and 70% expressed both IgM and IgA. The frequency of DEX-positive foci containing secreted IgA and IgM-IgA decreased as the age of the donors increased. The frequency of IgM-secreting foci remained constant at about 90% of DEX-positive foci regardless of donor age. The frequency of the MAID-defined cross-reactive idiotype CD3-2 and the EB3-16 idiotype changed very little in frequency with age, whereas the EB3-7 and LA4-8 idiotypes increased in frequency as donor age increased. Conversely, the SJL18-1 idiotope that was predominant at days 5 to 11 decreased in frequency relative to total DEX-positive foci as the age of the donors increased. The ratio of M104E-like and J558-like molecules from neonatal B cell precursors is reversed from that expressed by adult B cell precursors, and may reflect the preferential expansion of precursors bearing certain idiotypes by environmental antigens.     

Regulation of T15 idiotype dominance. II. Genes unlinked to the Igh locus regulate T15 dominance of the secondary adoptive transfer response to phosphocholine

We have studied the idiotype and fine specificity of the secondary immune response to phosphocholine (PC) in C57BL (B10, B10.D2, and B.C8) and BALB (BALB/c, BAB-14, and C.B20) congenic strains of mice. In vivo IgM responses of mice from these two genetic backgrounds differed in their T15 idiotypic representation. BALB strains expressed the T15 idiotype on greater than 90% of their IgM, PC-specific plaque-forming cells (PFC), whereas C57BL strains expressed the T15 idiotype on approximately 50% of their IgM PFC. All strains examined expressed greater than 75% PC-inhibitable, VHPC idiotype-positive, IgM PFC. The IgG3 and IgA memory responses were similar to the IgM memory response; BALB strains produced a higher proportion of T15+ PFC than C57BL strains; however, the majority of IgG3 and IgA PFC in all strains were VHPC+, and PC-inhibitable. In contrast, the IgG1 memory response was not dominated by T15+, VHPC+, PC-inhibitable PFC in any of the strains tested. The IgG1 PFC required nitrophenylphosphocholine (NPPC) for efficient inhibition. The IgG2 memory response generally mimicked the IgG1 response with respect to idiotype and specificity. These data demonstrate that the representation of the T15 idiotype in the anti-PC immune response is determined by genes outside both the MHC and Igh genetic loci. Control of T15 expression in secondary IgM, IgG3, and IgA anti-PC responses was examined by using a cell-mixing protocol with primed T and B cells from BALB/c and B10.D2 mice. T15 representation in these responses was determined by the genotype of the B cell, not by the genotype of the helper T cell. Similarly, the B cell genotype was responsible for the idiotypic profile of a primary, in vitro, T-dependent, anti-PC response.     

Variations in the responses of C57BL and a mice to sheep red blood cells: II. Analysis of plaque-forming cells

The number of direct and indirect plaque-forming cells (PFC) and the serum hemolytic activity was determined for A/He, C57BL/6J, and B6AF1 mice responding to multiple injections of sheep red blood cells (SRBC). Although the kinetics of the primary response differed, all mice had high numbers of both direct and indirect PFC and low-titered 2-mercaptoethanol (2-ME) sensitive serum antibody. Following multiple SRBC injections, the A/He spleens contained predominantly IgG producing PFC. Their serum antibody activity was resistant to 2-ME signifying the presence of IgG. The serum activity of both the C57BL/6J and B6AF1 mice was sensitive to 2-ME (IgM antibody) over the course of immunization, and although there was a definite IgM PFC memory response, the presence of 7S memory PFC was questionable. The results are discussed in terms of the maturation of the antibody response to SRBC and of the question of the postulated IgM and IgG switch.     

Expression of GAT-715 idiotype by GAT-specific plaque-forming cells from various strains of mice

The splenic plaque-forming-cell (PFC) response of mice to immunization with pneumococcal capsular polysaccharide (SSS-III), coupled with T-cell activation by phytohemagglutinin (PHA), is characterized by enhanced numbers of IgG-producing cells, largely restricted to the IgG2a and IgG2b subclasses. In contrast, immunization with SSS-III alone results in low numbers of IgG-producing cells, fairly evenly distributed among the subclasses IgG1, IgG2a, IgG2b, and IgG3. The enhanced IgG response and a concomitantly enhanced IgM response are T-cell dependent and occur only if PHA is given 2 days after SSS-III immunization. The absence of immunologic memory to SSS-III in mice previously immunized and treated with PHA implies that enhanced IgG production results from the activation of amplifier T cells and not the helper T cells which are required for memory.     

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)     

Cellular requirements for the expression of IgM. Immunological memory in vitro

In vitro culture techniques have been used to compare the direct (IgM) plaqueforming cell (PFC) response to heterologous erythrocytes (RBC) by normal mouse spleen cells and spleen cells from mice injected intravenously with 5 × 10⁴ RBC ten days previously [low dose primed (LDP)]. Although LDP mice fail to undergo a significant primary PFC response, their spleen cells are capable of a secondary or enhanced PFC response in vitro. The secondary PFC response is shown to be a function of: (A) an increase in the frequency of immunocompetent cells or units (IU) due to in vivo priming, and (B) an increased number of PFC generated per IU subsequent to in vitro stimulation. The latter increase is shown to be mediated through a shorter PFC doubling-time during logarithmic expansion of the PFC population. Analysis of nonadherent spleen cell dose response experiments indicate that two nonadherent cell types interact in the secondary response. Subsequent cocultivation experiments suggested that both of these cell types must be “primed” to allow induction of a secondary response. Although adherent cells are required for the secondary response, normal splenic adherent cells serve as equivalent substitutes for LDP adherent cells.     

GM-CSF augments the immunosuppressive capacity of neonatal spleen cells in vitro

Addition of exogenous granulocyte-macrophage colony stimulating factor (GM-CSF) to cultures of adult murine spleen cells with sheep red blood cells (SRBC) results in an augmented plaque forming cell (PFC) response. The influence of GM-CSF on the ability of neonatal spleen cells to suppress the anti-SRBC plaque forming response of adult spleen cells was tested by adding GM-CSF to cultures of neonatal and adult spleen cells. The suppressive capacity of the neonatal spleen cells was augmented by exogenous GM-CSF. The augmented suppression of the neonatal spleen cells was dependent on a G-10 adherent population since the addition of GM-CSF to cultures containing G-10 passed neonatal spleen cells resulted in an augmented PFC response and not suppression. Neonatal splenic glass adherent cells were also capable of suppressing the response. Neonatal spleen cells or purified neonatal glass adherent spleen cells cultured in the presence of GM-CSF had markedly increased levels of PGE2 in the culture supernatant. Neonatal spleen cells cultured with GM-CSF had increased numbers of morphologically identifiable macrophages after 48 hr of culture. Both irradiation and G-10 passage of the neonatal spleen diminished the numbers of macrophages formed in response to GM-CSF, and both of these manipulations resulted in reversal of suppression in response to GM-CSF. Thus, the augmented suppressive capacity of neonatal spleen cells in response to GM-CSF is probably mediated by its ability to drive monocyte to macrophage differentiation as well as increase the suppressive capacity of the existing neonatal splenic macrophages by increasing their production of PGE2.     

Complement-dependent and -independent pathways of T cell-B cell cooperation.

BDF1 mice treated with CoV had markedly reduced levels (less than 20%) of native serum C3 32 hr later, whereas the frequency of splenic CR+ cells was normal. CoV treatment before immunization reduced the IgM PFC response to a T-dependent antigen (TNP-SRBC) by more than 60%. Inclusion of highly specific anti-C3 antibody had no effect on the T-dependent IgM response of CR- B cells. The residual PFC responses in cultures of unfractionated spleen cells treated with anti-C3 could be largely or completely accounted for by CR- B cells in the cultures. The effect of anti-C3 antibody was not due to cytotoxicity. These data collectively indicate that the effect of CoV on T-dependent antibody responses is due to decreased C3 in serum rather than to interaction of C receptors directly with CoV or with C3 cleavage products. They suggest the existence of at least two distinct pathways of T-B cooperation, one in which C3 is an obligatory participant and another in which it may be uninvolved.     

Primary in vitro immunogenicity of liposomal model membranes in mouse spleen cell cultures.

Neither 2,4-dinitrophenyl-6-N-aminocaproylphosphatidylethanolamine (DNP-Cap-PE) nor fluoresceinthiocarbamylphosphatidylethanolamine (F1-PE) induces hapten-specific plaque-forming cells (PFC) when incubated with suspensions of spleen cells from unimmunized C57BL/6J mice. However, PFC are produced after incorporation of these synthetic lipid antigens into liposomal model membranes. The in vitro response is characterized by the following: a) it is time and dose dependent; b) the frequency of IgM PFC exceeds IgG PFC; c) both nonadherent and adherent cells are required (2-mercaptoethanol can replace the requirement for adherent cells in some experiments); d) depletion of thymus-derived cells by treatment with anti-theta antiserum plus complement does not diminish the response; e) spleen cells from nude BALB/c mice also produce PFC. Thus, the essential features of the in vivo immunogenicity of DNP-Cap-PE and F1-PE sensitized liposomes, which have been previously described, can be replicated in an in vitro cell culture system.     

Antibody formation in mouse bone marrow. IX. Peripheral lymphoid organs are involved in the initiation of bone marrow antibody formation.

Mouse bone marrow is barely capable of plaque-forming cell (PFC) activity during the primary response to sheep red blood cells (SRBC). However, during secondary-type responses, it becomes the major organ, containing IgM, IgG, and IgA PFC. In the present paper, the influence of splenectomy (Sx) upon the secondary bone marrow PFC response to SRBC was investigated. When previously primed mice were splenectomized just before the second intravenous (iv) injection of SRBC, the effect of Sx upon the height of the bone marrow PFC response was dependent on the booster dose. Sx just before a booster of 10⁶ SRBC iv almost completely prevented bone marrow PFC activity, whereas an iv booster dose of 4 × 10⁸ SRBC evoked a normal IgM, IgG, and IgA PFC response in Sx mice. Apparently low doses of iv administered antigen require the spleen in order to evoke antibody formation in the bone marrow. Experiments with parabiotic mice, consisting of Sx and sham-Sx mice, showed that this facilitating influence of the spleen upon bone marrow antibody formation occurs via the blood stream. In a subsequent study, it was investigated whether the spleen is required throughout the bone marrow PFC response or only during the few days of the initiation phase. Therefore, mice were splenectomized at different intervals after a booster injection of 10⁶ SRBC iv. It appeared that Sx 2 days after the booster injection could still prevent the normal bone marrow PFC activity, whereas Sx at Day 4 could no longer do so. Apparently, after an iv booster injection, the spleen is only required for initiation of the bone marrow PFC response and not for the maintenance of this PFC activity thereafter.     

Selective immunomodulation by the antineoplastic agent mitoxantrone. I. Suppression of B lymphocyte function

Novantrone mitoxantrone, an antineoplastic agent with antiproliferative properties, is under investigation as an immunomodulating agent. The impact of mitoxantrone treatment on B lymphocyte reactivity is presented here. Administered i.p. in H2O at a dose of 0.5 mg/kg, daily for 14 days, mitoxantrone abrogated both the in vivo antibody response (to ovalbumin) and the in vitro plaque-forming cell (PFC) response (to SRC). In addition to the effects on thymus-dependent reactivity, PFC responses to the thymus-independent antigens TNP-LPS and TNP-Ficoll were also inhibited when tested in vivo or in vitro. B cells were identified as a target for the suppressive activity of mitoxantrone by using T cell-replacing factor to reconstitute the in vitro anti-SRC PFC response of a T lymphocyte-depleted spleen cell preparation. LPS-induced B cell mitogenesis was largely inhibited by mitoxantrone treatment. However, depletion of Sephadex G-10-adherent cells significantly restored the proliferative response. Flow cytometric analysis revealed a dramatic decrease in splenic B lymphocyte content. Therefore, mitoxantrone exerted a potent suppressive influence on the humoral immune system through a direct reduction in B cell number augmented by macrophage-mediated inhibition of B cell proliferation.     

Immunoregulation in the rat: ontogeny of B cell responses to types 1, 2, and T-dependent antigens

The development of rat B cells has been examined in neonatal and adult Fischer rats through the use of type 1 (TNP-Brucella abortus), type 2 (TNP-LPS(Ph), TNP-Ficoll) and T cell-dependent (TD) (SRBC) antigens. In vivo splenic PFC responses to TNP-Brucella abortus could be induced in newborn rats and by 12 days of age had reached adult levels. In contrast, the responses to the type 2 and TD antigens were 30% and 70%, respectively, of the adult levels at 30 days of age. Adoptive transfer of the B cells from neonatal and young rats into irradiated adult hosts demonstrated that the kinetics in the development of responses to these antigens (early for type 1, intermediate for TD, and late for type 2) were not due to limiting accessory cell or T cell help in immature rats. In vitro cultures of purified B cells from neonatal and adult rats were responsive to TNP-BA and TNP-LPS(Ph) but not to TNP-Ficoll and SRBC. However, the addition of spleen cell-derived Con A supernatant to the B cell cultures resulted in responses to all four antigens, which arose as a function of B cell age, with kinetics that were identical to those observed in vivo. Fluorescent staining of B cells from rats of various ages for cell surface IgM and analysis on the fluorescence-activated cell sorter (FACS) revealed that all splenic B cells from rats 4 days of age expressed a relatively high level of sIgM, and that a subpopulation that expressed a relatively low level of sIgM increased with age until it represented approximately 50% of the adult splenic B cells. Challenging Con A supernatant-supplemented cultures of FACS-prepared low sIgM+ and high sIgM+ cells revealed that B cells responsive to TNP-Ficoll were confined to the ontogenically late-arising low sIgM+ subpopulation but that B cells responsive to TNP-BA, TNP-LPS(Ph), and SRBC were present in both subpopulations.     

Delayed maturation of the antibody response to type 2 thymus-independent antigens in a partially inbred strain of chicken

The ontogeny of antibody responses to trinitrophenylated (TNP) thymus-independent (TI) antigens was compared in two partially inbred strains of chicken: the SC strain (B2/B2 genotype) and the FP strain (B15/B22 genotype). In the SC chicken, maturation of both the splenic anti-TNP plaque-forming cell (PFC) response and the 19S hemagglutinating antibody response to TI type 2 (TI-2) antigens, TNP-Ficoll and TNP-dextran, were delayed to a significantly later time in ontogeny (20 wk of age) than in the FP chickens (9 wk of age). Four- to 6-wk-old SC chickens were virtually immunologically unresponsive to stimulation with TI-2 antigens. The TI-1 antigen TNP-Brucella abortus was equally immunogenic in both FP and SC chickens of different age groups tested. Kinetic studies of the primary PFC response to TNP-Ficoll in immunologically mature chickens of the SC and FP strains demonstrated a peak PFC response 4 days after antigen injection, followed by a rapid decline in numbers of splenic PFC/spleen on day 6. The results of these studies are discussed in relation to earlier observations that suggested there may be a delay or a defect in the ontogeny of the thymus in the SC chicken.     

IgA anti-dextran B1355 responses.

Injection of mice bearing the Ig-1a allotype with dextran B1355 results in an IgM antibody response that is generally regarded as thymus independent. Moreover, the antibody is directed to alpha[1,3] determinants on dextran B1355 and shares cross-reacting idiotypic determinants with a lambda 1 IgA (J558) myeloma protein as well as a lambda 1 IgM (MOPC 104E) myeloma protein. In this study, we show that BALB/c (Ig-1a) mice injected with dextran B1355 produced highly significant IgA anti-dextran responses with specificity directed to the alpha[1,3] epitope. Kinetics of the IgA anti-dextran response in BALB/c mice paralleled kinetics of the IgM response. However, the magnitude of the IgA response was markedly T cell dependent and age dependent.