Lectin-induced modulation of the antibody response to type III pneumococcal polysaccharide

Several lectins were tested for their capacity to alter the antibody response to type III pneumococcal polysaccharide (SSS-III). The antibody response was enhanced by concanavalin A (Con A), phytohemagglutinin (PHA), as well as lectins from Phytolacca americana (Pa-2), Pisum sativum (PSA), and Lens culinaris (LCH), when these lectins were given 2 days after immunization with SSS-III; however, suppression was obtained when Con A and Pa-2 were given at the time of immunization. By contrast the lectins from Vicia villosa (VVL) and Bauhinia purpurea (BPA) did not alter the antibody response. Since the lectins PSA and LCH bind to the same monosaccharide as Con A, whereas the other lectins bind to different monosaccharides, these findings indicate that there is no relationship between nominal monosaccharide specificity and the capacity to modulate the antibody response. Substantial increases in the magnitude of the IgG₁ antibody response was noted after the administration of Con A whereas profound enhancement of IgG_2a antibody response was noted after PHA was given.     

Hapten-IgG-induced suppression of the in vitro antibody response: role of hapten density and of antigenic challenge.

We have studied the suppression of the in vitro antibody response of mouse spleen cells to the trinitrophenyl (TNP) hapten by conjugates of TNP-human IgG (TNP-HGG). Normal mouse spleen cells were incubated with conjugates of HGG and of HGG fragments, with different hapten densities. They were then challenged with either a T-dependent or a T-independent antigen. Highly substituted (12 mol of TNP/mol of HGG) conjugates induced a dose-dependent suppression, apparent after short-term incubation at 4 °C, of both T-dependent and T-independent responses. Conjugates of Fab′₂ and Fab′ were as suppressive as conjugates of IgG, whereas conjugates of albumin, aggregated IgG, and β2 microglobulin lacked suppressive activity. In contrast, the lightly substituted conjugates TNP₈-HGG and TNP₂-Fab′₂ induced a time-dependent suppression, affecting only the T-dependent response. This suggests that the suppressive effect of hapten-IgG conjugates is mediated by two different mechanisms according to the density of hapten on the IgG carrier. When these conjugates are used as tolerogens in the in vivo situation, both mechanisms would operate to a variable extent, and this could account for the remarkable tolerogenic properties of hapten-IgG conjugates.     

Mechanisms of protective immunity against Schistosoma mansoni infection in mice vaccinated with irradiated cercariae: I. Analysis of antibody and T-lymphocyte responses in mouse strains developing differing levels of immunity

The kinetics of cellular and humoral responses directed against schistosomula were examined in mice of three inbred strains which demonstrate differences in the degree of resistance induced by immunization with irradiated cercariae. T-Cell reactivity was observed during the first 4 weeks after vaccination but declined to control levels thereafter. Anti-schistosomulum antibody was first detected 2 weeks after vaccination, peaked by 6 weeks, and persisted as late as 15 weeks. In sera obtained at 6 weeks, antibody activity was detected in affinity chromatography-purified fractions containing IgM, IgA, IgG₁, IgG_2a, and IgG₃ immunoglobulins. In general, the cellular and humoral responses observed in C57B1/6J mice, which consistently developed a high level of immunity after vaccination, were not significantly different from those observed in C3H/HeJ or CBA/J mice, which achieved only low to moderate levels of immunity. Thus, although antibody production appears to correlate more closely than T lymphocyte responsiveness with the typical long-term resistance pattern observed in this model, the absence of striking differences in parasite-specific antibody levels between mice of these different strains suggests that additional mechanisms may be involved in the development of immunity after vaccination.     

Immunoglobulin isotype distribution of malaria-specific antibodies produced during infection with Plasmodium chabaudi adami and Plasmodium yoelii

The antibody response of mice to Plasmodium chabaudi adami and Plasmodium yoelii has been compared using a solid phase isotype-specific radioimmunoassay and sodium dodecyl sulfatepolyacrylamide gel electrophoresis. Serological cross-reactivity between these parasites was substantial. Studies using a radioimmunoassay detecting all classes of malaria-specific antibody demonstrated that during the early part of infection it was not possible to distinguish between homologous and heterologous reactions. Immunoprecipitation and sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed that 50% or more of the protein antigens detected were apparently shared by both parasites although the intensity of bands was always greater with homologous reactions. However, the distribution of isotypes in the antibody (Ab) response differed in the two infections. P. chabaudi infections were characterized by a predominant and persistent IgM response, moderate IgG₂ and IgG₃ and little significant IgG₁ response during a primary infection. By contrast, IgM antibodies were transient in P. yoelii infection, IgG₂ was the predominant isotype, and both IgG₁ and IgG₃ antibodies were present during a primary infection. These differences in isotypes were also detected when sera were tested on the heterologous antigen extracts suggesting that antigens shared by P. chabaudi and P. yoelii do not necessarily induce similar antibody responses in the two infections.     

Monoclonal antibody against K562 cell line accelerates killing of the target cells by large granular lymphocytes

A monoclonal antibody (MoAb 11-4) was raised against K562, a human erythroleukemia cell line sensitive to natural killer cell-mediated cytotoxicity (NK-CMC). Immunological analysis revealed MoAb to be IgG_2b. Alone, the MoAb was not cytotoxic for K562 and did not bind to the effector cells, but the addition of this antibody to macrophage-depleted human peripheral blood lymphocytes increased killing of K562 in a 4-hr NK-CMC assay. The maximum increase in NK-CMC was observed when MoAb 11-4 was added to target cells prior to the formation of effector/target cell conjugates. This effect was dose dependent, was specific for K562, and, contrary to conventional antisera, occurred at very low concentrations of MoAb. When MoAb was added either to Percoll-purified large granular lymphocytes (LGL) or to LGL-depleted lymphocytes, only the latter demonstrated a significant increase in the killing of K562 in a 4-hr chromium release assay. Kinetics studies revealed that although the overall LGL-mediated lysis was only slightly increased at 4 hr, the maximum lytic activity was reached within 2 hr. These studies suggest that (1) human LGL and LGL-depleted cell populations bear Fc receptors for mouse IgG_2b and (2) although the cytotoxic activities of both cell populations are increased by treatment with MoAb 11-4, the kinetics of this increase are different.     

Trichinella spiralis: anaphylactic antibody formation and susceptibility in strains of inbred mice.

The anaphylactic antibody response of various strains of inbred mice of different H-2 specificities was investigated using the passive cutaneous anaphylactic technique (PCA) for the detection of the antibody response. Neither IgC₁ nor reaginic antibody were detected in serum samples obtained at the end of the first week of infection with Trichinella spiralis. Subsequently, all animals had detectable IgG₁ antibodies, although in some strains the titers were very low. Reaginic antibody was detected in relatively high titers in C57L, A, and DBA/1 mice. Two other strains were very poor responders (SJL and AKR). In most strains, reagin and IgG₁ remained detectable for 14 wk or longer. The pattern of response of all strains was very reproducible, indicating genetic control of the anaphylactic antibody production to the infection. In F₁ hybrids obtained from crosses between good and poor anaphylactic antibody responders, intermediate levels of both antibody classes were detected.Adult worm recovery rates were established at various points during the intestinal phase of infection, and no correlation between worm numbers and reaginic antibody titers in the various strains of mice could be demonstrated. There were noticeable differences in larval yields obtained after muscle digestion of mice belonging to the different inbred strains. In fact, we generally observed an inverse relationship between the number of larvae recovered from a given strain and their reaginic antibody titer.The intravenous injection of newborn larvae (NBL), obtained upon in vitro incubation of adult worms, produced detectable antibodies only in mice of the DBA/1 strain. These antibodies were consistently of low titer and became detectable only after the administration of two additional injections of NBL. This contrasted with the results observed after “per os” infection of DBA/1 mice, where high titers of these antibodies were always obtained, in spite of comparable ratios of muscle larval yield.     

Ascaris suum: homocytotropic antibody responses in mice.

Homocytotropic antibodies in the sera of CD-1 and DBA/1 mice infected with larval A. suum were titered by PCA reactions. IgG₁ and reaginic antibody responses were similar in both strains of mice. With a dose of 8000 to 10,000 embryonated eggs, reaginic antibody was detected during the second week and IgG₁ antibody during the third week of infection. Doses of 1500 to 5000 eggs gave delayed antibody responses or did not induce a detectable response, although an anamnestic response followed a challenge inoculation even when no detectable antibody was observed in initial infection. Larval A. suum infections in two strains of mice did not potentiate a reaginic response to ovalbumin.     

Basal immunoglobulin serum concentration and isotype distribution in relation to the polygenic control of antibody responsiveness in mice

Serum Ig concentration and isotype distribution were determined in the high (H) and low (L) responder lines selected for antibody response to complex immunogens. Data were recorded in normal and postimmunization sera from the H and L lines produced by five independent selective breedings (selections I, 11, III, IV, and V). Ig levels were much higher in H than in L mice of all the selections. In four selections this interline difference increased further after immunization with the selection antigens. This is in agreement with the general effect of the polygenic control of antibody responses operating in H and L lines. The Ig isotype profiles of normal sera were different in each line; however, similitudes were noticed between H and L lines in selections I and If. In contrast, in selections III, IV, and V a similar interline difference was observed: the lack of IgG2a isotype in L lines only. After immunization there were minor alterations of the isotype profiles except in the H lines of selections III and IV, in which a clear inverse modification of IgG₁ and IgG_2a proportions occurred. The characteristic pattern of each selection may be partially dependent on isotype-restricted regulatory effects in relation to the immunization procedure used for selective breeding.     

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.     

2B4 Is Dispensable for T-Dependent B Cell Immune Responses,but Its Deficiency Leads to Enhanced T-Independent Responses Due to an Increase in Peritoneal Cavity B1b Cells

The signaling lymphocyte activation molecule (SLAM) family plays important roles in adaptive immune responses. Herein, we evaluated whether the SLAM family member 2B4 (CD244) plays a role in immune cell development, homeostasis and antibody responses. We found that the splenic cellularity in Cd244 ^-/- mice was significantly reduced due to a reduction in both CD4 T cells and follicular (Fo) B cells; whereas, the number of peritoneal cavity B cells was increased. These findings led us to examine whether 2B4 modulates B cell immune responses. When we examined T-dependent B cell responses, while there was no difference in the kinetics or magnitude of the antigen-specific IgM and IgG₁ antibody response there was a reduction in bone marrow (BM) memory, but not plasma cells in Cd244 ^-/- mice. When we evaluated T-independent immune responses, we found that antigen-specific IgM and IgG₃ were elevated in the serum following immunization. These data indicate that 2B4 dampens T-independent B cell responses due to a reduction in peritoneal cavity B cells, but has minimal impact on T-dependent B cell responses.     

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 toxicity of neocarzinostatin-monoclonal antibody conjugates to the antigen-bearing human melanoma cell line in vitro

Summary Monoclonal antibodies (IgG₁) against high molecular weight antigen A-1-43 on human melanoma cell line A-375 were successfully linked to the anti-tumour protein neocarzinostatin (NCS) using the heterobifunctional reagent N-succinimidyl 3-(2-pyridyldithio)-propionate (SPDP). The conjugate retained both the reactivity of the antibody and the toxicity of the drug. The antigen-bearing cell line A-375, antigen-lacking cell line MeWo and normal skin fibroblasts were exposed to NCS-monoclonal antibody conjugates. As negative control, cells were also treated with free NCS and NCS coupled to normal mouse IgG₁ antibodies. Inhibition of ³H-thymidine uptake after treatment was used to measure the biological activity of the cytotoxic drug complex or substance, respectively.Comparing the inhibition dose for 50% uptake (ID₅₀) it was found that the monoclonal antibody-drug complex is about 100 times more toxic for the antigen-bearing cell line than free NCS or normal mouse IgG₁-NCS. This high toxicity is due to a local increase of drug concentration on these cells. With the two cell lines lacking the appropriate antigen no significant differences in the ID₅₀ values were observed. A selectivity factor of 40–50 was obtained by comparing the cytotoxic effect of the monoclonal antibody-NCS conjugate upon the antigen-bearing as opposed to the antigen-lacking cell type. These data demonstrate, that the toxicity of NCS can be directed by monoclonal antibodies to human tumour cells carrying the corresponding surface antigen.     

The effects of carrier-specific helper T-cell tolerance on antibody avidity in the anti-hapten response.

Rats rendered tolerant to ultracentrifuged sheep γ-globulin (SGG) have been shown to make a poor anti-trinitrophenyl (TNP)-specific antibody response upon challenge with TNP-SGG in complete Freund's adjuvant (CFA). We have been able to use this carrier-tolerance system in studying specific helper T-cell unresponsiveness to IgG and IgM antibody responses. By using the plaque inhibition technique to measure antibody avidity, we found that there appears to be no difference in the avidity of antibody responses to TNP between the SGG-tolerant and control groups when both are challenged with TNP-SGG in CFA. This was found to be true in both the 19 and 7S antibody responses in vivo as well as in an adoptive transfer model. In addition, studies on the maturation of 19 and 7S antibody responses showed no differences in antibody avidity between carrier-tolerant and control groups. These findings imply that carrier-specific helper T cells do not play a controlling role in determining whether high- or low-avidity hapten-specific B-cell precursors will proliferate in response to challenge with a hapten-carrier conjugate.     

Capillaria hepatica: Granuloma formation to eggs: III. Anti-immunoglobulin augmentation and reagin activity in mice

Sera from mice with primary and secondary Capillaria hepatica egg granulomas were examined for 48-hr homologous PCA activity and for the presence of IgM, IgG₁, and IgG₂ using a microtiter anti-globulin augmentation assay following indirect hemagglutination testing. All three antibody types assayed were present. Secondary granuloma formation produced an antibody response characterized by the initial production of IgM followed by IgG₁ and IgG₂ during the latter phase of the test period, however primary granulomatous sera demonstrated a more varied antibody response with the presence of all three during the entire test period. Forty-eight-hour PCA tests demonstrated the presence of reagin activity in sera from granulomatous and infected mice. Reagin activity occurred more frequently in primary than secondary granulomatous mice. These studies thus confirm the presence of antibody during granuloma formation to C. hepatica eggs and conclusively demonstrate the presence of at least two classes of antibody.     

Idiotypic regulation of mouse anti-H-2 antibody responses

Mouse-immunoglobulin (MIg) tolerant rabbits immunized with mouse H-2 antibodies produced anti-idiotype antisera, which were reactive towards specific B- and T-cell receptors. One such rabbit antiserum (from rabbit 5936) defines a family of idiotypes (Id) designated 5936-idiotypes (Rubin et al. 1979). The present experiments were performed in order to establish (1) the nature of 5936-Id⁺ serum molecules, (2) the specificity of 5936-Id⁺ serum molecules, (3) the association of the 5936-Id genes to allotype and/orH-2 genes and (4) the immunological role of 5936-Id⁺ serum molecules. A sensitive, radioimmunoassay employing¹²⁵I-labelled-F(ab)₂ fragments of B6 anti-B10.BR MIg pool, 5936 antiserum, and a sheep anti-rabbit immunoglobulin antiserum, was used.—The results suggested that 5936-Id⁺ serum molecules were exclusively MIg, and that they were mainly of the IgG₁ class. Such molecules were induced in B6 mice (H-2 ^b /Ig-1 ^b ) upon immunization with H-2^k but not with H-2^q alloantigen or conventional antigens. The 5936-Id were found to be associated with Ig-1^b allotypes and theH-2 ^b complex may contain immune response (Ir) genes which, in comparison withIr genes inH-2 ^d andH-2 ^s , favor the expression of 5936-Id.—Adsorption of 5936-Id⁺ B6 anti-CBA MIg preparations on CBA (IA^k) spleen cells demonstrated that CBA antibodies were 5936-Id^?. It is dicussed whether 5936-Id⁺, IgG₁ molecules in B6 anti-CBA sera are anti-(anti-CBA) antibodies or nonspecific antibodies, the production of which is augmented by immunization with IA^k alloantigen.     

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.     

Modulation of mouse anti-SRBC antibody response by placental extracts

Mouse placental extracts (PE) and corresponding Sephadex G-200 fractions were administered to isogeneic CBA mice along with an optimal immunizing dose of SRBC. Spleen cells were harvested 8 days later and transferred to CBA recipients, subsequently immunized with SRBC. The immunoregulatory activity of spleen cells from PE-treated donors was compared to cells from liver extract (LE)-treated controls or from mice immunized with SRBC only, using Cunningham's PFC direct and indirect tests. Within the dose range used, selective modulatory activities were obtained with cells from PE, but not from LE, treated mice, the latter being comparable to cell transfer effects from donors immunized with SRBC only. Spleen cells from animals injected with low doses of PE (0.25 to 4 mg per mouse) added to immunizing SRBC had a suppressive effect on the primary IgM response of recipients immunized against SRBC. In contrast, when SRBC were given to donor animals with higher doses of PE (8 to 13 mg), transferred spleen cells potentiated the IgM response of the recipients. These opposite suppressive and potentiating activities were found in distinct Sephadex G-200 fractions of 40 and 60 kDa, respectively. When the effect of PE treatment was tested within the same animal, the indirect secondary PFC response following a challenge with SRBC was significantly modified. We observed an overall suppression of the different isotypes after treatment with lower doses of PE or with its 40-kDa fraction. PE doses of 0.5 to 2 mg resulted in a stronger inhibition of IgM than IgG₁ production. This phenomenon was also obtained with the 40 KDa fraction. IgG₂ responses were significantly reduced by all doses of this fraction. In contrast, all doses of the 60-kDa fraction gave a strong stimulation of IgG₂ and IgM responses and a constant suppression of the IgG₁ response. This shows a clear dissociation between IgG₁ and C'-fixing (IgM, IgG₂) antibody classes as far as the influence of placental substances is concerned in their regulation. These data emphasize the relevance of isogeneic placental products as a useful physiological material capable of modulating xenogeneic immune responses (as well as allogeneic systems).     

Direct and indirect plaque forming cells in extrapulmonary lymphoid tissue following local vs systemic injection of soluble antigen

AKR strain mice were immunized with solubilized SRBC stroma either by direct injection into the lower respiratory tract or intravenously via the tail vein. The number of plaque forming cells (PFC) in the draining plumonary lymph node (tracheobronchial node) and spleen were determined by direct (IgM) and indirect IgG₁, IgG_2b, IgA) plaque assays.Intravenously administered antigen induced an initially strong IgM response in the spleen which was subsequently followed by antibody of the IgG₁, IgG_2b, and IgA classes of immunoglobulins. The tracheobronchial lymph node contained a minimal number PFC representing all four types of immunoglobulins studied. Conversely, following a single local injection of antigen directly into the lower respiratory tract, the tracheobronchial node responded with relatively high concentrations of PFC of all classes. The response in the spleen, although higher than background, was barely detectable. The splenic response to locally administered antigen was, however, considerably augmented as a result of a second local injection given 45 days after the initial stimulation. Under these conditions, IgG₁ IgG_2b, and IgA were represented in both tissue sites by sharp increases in the number and a decrease in the time of appearance of their respective antibody forming cells. Comparable changes were not noted for the case of IgM.Serum hemagglutination titres following a single injection by either route did not vary significantly during the time course of the experiment (28 days). The sera from locally immunized mice were treated with the reducing agent dithiothreitol and hemagglutination titres, before and after treatment, were compared. The major serum activity observed during the first 10 days following injection was affected by reduction and could therefore be assigned to high molecular weight antibody (19S, 13S). Subsequent titres (Days 13–26) were less susceptible to DTT and are considered to represent low molecular weight immunoglobulins (7S).     

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.     

Effects of the MER tubercle bacillus fraction on the production of antibodies in vitro: I. Effect on the primary response

The effect of the methanol extraction residue (MER) fraction of BCG tubercle bacilli on the primary antibody response in vitro to sheep red blood cells (SRBC), TNP conjugates, and the monovalent hapten DNP-glycine was studied. Addition of MER to whole splenocyte cultures simultaneously with antigen presentation potentiated the antibody response to SRBC and TNP-SRBC, and facilitated reactivity to DNP-glycine; there was no effect on the response to the T-independent entity TNP-LPS (lipopolysaccharide from E. coli 055-B5). Immunopotentiating activity of MER for SRBC and DNP-glycine was also evident in macrophage-depleted cultures. Peritoneal exudate cells (PEC) taken from MER-treated donors were more efficient than PEC from untreated donors in reconstituting antibody formation to SRBC by macrophage-depleted spleen cell populations. The results obtained indicate that activation of both macrophages and of certain lymphocyte population(s) by MER may play a role in the potentiation of antibody responsiveness in vitro by this agent.