Different effects of the capsular polysaccharide of Klebsiella pneumoniae on the functions of various subpopulations of B cells in the immune response of mice to T-dependent antigen.

Using the capsular polysaccharide of Klebsiella pneumoniae (CPS-K) as a polyclonal B-cell activator (PBA) and sheep red blood cells (SRBC) as a T-dependent antigen, we studied the effects of PBA on the functions of various subpopulations of B cells in the immune response of mice to T-dependent antigen. Antibody-forming cells (AFC) of IgM and IgG types were estimated as anti-SRBC direct and indirect plaque-forming cells (PFC), and the B cells with precursor activities involving generation of AFC and supplementing new B cells as rosette-forming cells (RFC) of the B-cell type. Stimulation of normal mice by CPS-K caused a definite increase in the number of direct PFC but not in that of indirect PFC and RFC in the spleens. The responsiveness of spleen cells of CPS-K-treated mice to generate PFC and RFC responses to a subsequent injection of SRBC was lower than that of CPS-K-untreated normal mice. In this case, the responsiveness to generate RFC and indirect PFC was inhibited more strongly by CPS-K than that to generate direct PFC. When CPS-K was injected into normal mice simultaneously with SRBC, CPS-K never decreased but increased the levels of PFC and RFC responses to SRBC. In the spleens of SRBC-primed mice, the number of RFC was markedly decreased following injection of CPS-K, the number of direct PFC was increased only slightly and the number of indirect PFC was increased very slightly. The responsiveness of spleen cells of these CPS-K-treated SRBC-primed mice to generate secondary PFC and RFC responses to a subsequent injection of SRBC was much lower than that of CPS-K-untreated SRBC-primed mice. In this case, the responsiveness to generate the secondary RFC and indirect PFC responses was more strongly inhibited by CPS-K than that to generate the secondary direct PFC response. When CPS-K was injected into SRBC-primed mice simultaneously with the secondary injection of SRBC, there were marked decreases in the level of the secondary RFC response and slight decreases in that of the secondary indirect PFC response, but little change in that of the secondary direct PFC response. From these results it has been concluded that CPS-K provides the positive signal (the minor action) and the negative signal (the major action) to various subpopulations of B cells functioning at various stages of the immune response to T-dependent antigen in different ways, and acts to regulate the levels of B-cell responses to the antigen-mediated positive signal.     

Antibody formation in mouse bone marrow. VIII. Dependence on potentially circulating memory cells: a study with parabiotic mice.

Mouse bone marrow barely contains antibody-producing plaque-forming cells (PFC) during the primary response to sheep red blood cells (SRBC). However, during the secondary response, the number of IgM, IgG, and IgA PFC in the bone marrow can rise to a level which surpasses the number of PFC in all the other lymphoid organs together. In the present paper we investigated whether the capacity of immune mice to react upon a booster injection of SRBC with a bone marrow PFC response can be transferred from immune to nonimmune mice. Therefore, mice primed with SRBC 6 months previously and nonprimed syngeneic mice were joined for parabiosis and were separated from each other at various intervals after joining. These separated mice were subsequently immunized with SRBC. It was found that, after 3 weeks of parabiosis, the nonprimed members reacted upon an injection of SRBC with a bone marrow IgM, IgG, and IgA PFC response as high as did the previously primed members. Furthermore it could be demonstrated by means of cell transfer experiments that, after a period of parabiosis of 3 weeks, the bone marrow and spleen of the normal mice contained about as many memory cells as the bone marrow and spleen of the immune mice. These results suggest that antibody formation in mouse bone marrow is dependent on a population of potentially circulating memory cells.     

Differential effects of concanavalin A and phytohemagglutinin on murine immunity. Suppression and enhancement of humoral immunity.

The abilities of concanavalin A (Con A) and phytohemagglutinin P (PHA) to selectively induce different T-cell activities affecting humoral immunity were evaluated. The mitogens were intravenously injected before, with, or after injection of sheep red blood cells (SRBC) into mice, and the 3 to 6-day plaque-forming cell (PFC) responses were assessed. Mitogenic treatment differentially influenced the resultant in vivo PFC responses to SRBC. The in vivo suppressive effects induced by Con A were shown to be temporary; only the Day 4 PFC response was inhibited. Con A given 3 hr before, with, or after the antigenic challenge enhanced the PFC response. In contrast, PHA given at all intervals inhibited both the 4- and 5-day PFC response. Neither mitogen appeared to affect the kinetics of the in vivo PFC response to SRBC. Both mitogens enhanced in vivo DNA synthesis by the splenic cells, and Con A appeared biphasic in its stimulation. Con A-induced effects on the humoral immune response were short-lived and transient, while PHA induced a longer-lasting effect on humoral immunity.     

Structural and serological studies of lipopolysaccharides of Citrobacter O35 and O38 antigenically related to Salmonella

Abstract Lipopolysaccharide (LPS) was administered into sheep red blood cells (SRBC)-primed mice, and the effect of LPS on SRBC-specific memory cells was investigated. Spleen cells from SRBC-primed mice which were injected with LPS exhibited much lower in vitro secondary plaque-forming cells (PFC) responses to SRBC than those from untreated SRBC-primed mice. The in vitro anti-SRBC response of the spleen cells to LPS was also reduced. The combination experiments of B cells and T cells from SRBC-primed mice which were injected with or without LPS demonstrated that the reduction of immune responses to SRBC after administration of LPS was caused by the defect of SRBC-specific B memory cells, but not T memory cells. B cell type rosette-forming cells (RFC) for SRBC markedly decreased after injection of LPS, while PFC as antibody-forming cells did not increase subsequently. Therefore, the reduction of RFC was not due to their differentiation into PFC. The lymphoid follicles in the spleens from mice injected with LPS were stained positively by in situ nick end labeling specific for fragmented DNA. A large percentage of Ig⁺ spleen cells from SRBC-primed mice which were injected with LPS was also stained positively. The injection of glucocorticoids into SRBC-primed mice induced similar reduction of B memory cells. It was suggested that LPS might induce apoptosis of B memory cells and regulate B cell memory in antigen-nonspecific manner.     

Nonspecific Elicitation of Antibody-Forming Cells in the Mouse Spleen by Bacterial Lipopolysaccharide

Mechanisms of nonspecific elicitation of anti-sheep erythrocyte (SRBC) hemolytic antibody plaque-forming cells (PFC) in mouse spleens with an injection of bacterial endotoxin (lipopolysaccharide (LPS)) were studied in comparison with the genesis of naturally occurring ‘background’ PFC in normal mouse spleens and of rapidly arising PFC in mouse spleens after immunization with SRBC. The cytokinetic pattern of anti-SRBC PFC response after an injection of LPS was quite different from that of the response elicited after immunization with SRBC. In addition, even though LPS nonspecifically elicited anti-SRBC PFC response in mice, LPS could not confer any immunological memory on mouse immunocytes for a ‘secondary-type’ anti-SRBC PFC response to restimulation with LPS or SRBC. The administration of rabbit anti-mouse thymocyte immunoglobulin or anti-SRBC antiserum in mice markedly suppressed the PFC response after immunization with SRBC, but did not do so after stimulation with LPS. Neonatally thymectomized mice could still respond to stimulation with LPS, producing anti-SRBC PFC in their spleens. Injections of actinomycin D or cyclophosphamide into mice resulted in obvious reductions of the PFC responses elicited by either LPS or SRBC. However, injections of these immunosuppressive antisera or drugs did not affect the number of anti-SRBC PFC in normal mouse spleens. These results suggest that the geneses of anti-SRBC PFC developed under different conditions, i.e., background PFC, LPS-stimulated PFC, and antigen-stimulated PFC, are quite different from each other, and that the nonspecific elicitation of anti-SRBC PFC by LPS does not require the helper function of T lymphocytes. No obvious difference, however, was observed in the time of ontogenic maturation among these three different anti-SRBC PFC in the mouse spleens judging from when they were first manifested after birth.     

Relation between Enhanced Antibody Responses Elicited by Adjuvant Injection and Those Elicited by Secondary Antigenic Stimulation

An attempt was made to determine if there is any common mechanism in the enhanced antibody response caused either by injection of adjuvant, such as bacterial endotoxin (LPS) and complexed polynucleotides, or by secondary antigenic stimulation. LPS inoculated in mice 4 days before injection of sheep red blood cells (SRBC) and polyA:U invalidated the adjuvant effect of polyA:U injected together with SRBC, and the hemolysin plaque-forming cell (PFC) response of such mice was similar to that of the mice which received SRBC alone. When mice primed with SRBC 24 days in advance were injected with LPS and 4 days later re-stimulated with SRBC, their PFC response to the secondary stimulation was suppressed to less than one tenth of the normal secondary PFC response. The suppressive effect of LPS on the secondary antibody response was abolished if the serum collected from mice injected with LPS was given to the primed and LPS-injected mice at the time of the secondary antigenic stimulation. From these results we discussed the possibility that some common mediator might play a role in the enhanced antibody response elicited by either adjuvant injection or secondary injection of antigen.     

Studies on the Maturation of Immune Responsiveness in the Mouse

The ability of early post-natal mice to respond to sheep erythrocytes (SRBC) by formation of plaque-forming cells (PFC) was studied. When 1–2 day old BDF, mice were injected with SRBC, no PFC could be detected in their spleens five days after immunization. However, if animals were given a second injection of antigen two days after the initial immunization, PFC could be detected within five days of the initial injection. Experiments with other heterologous erythrocytes attest to the specificity of the two-injection schedule, and examination of a variety of strains of mice indicate that our findings may be generally applicable to the emerging immune system of the mouse.     

Ineffectiveness of Lipopolysaccharide for Preventing the Tolerance Induction in Bone Marrow-Derived Lymphoid Cells with Dinitrophenyl-Poly-l-(Glutamic Acid,Lysine)

The effect of endotoxin or lipopolysaccharide (LPS) on tolerance induction in bone marrow-derived lymphoid cells (B cells) was investigated. Dinitrophenylated amino acid copolymer-l-(glutamic acid, lysine) (DNP-GL) acts as a potent tolerogen on normal and DNP-primed B cells. LPS significantly enhanced the anti-sheep red blood cell plaque-forming cell (anti-SRBC PFC) response that occurred after the immunization with a low dose of SRBC. LPS did not induce the primary anti-DNP PFC response after the injection of DNP-GL, nor did it prevent the tolerance induction in normal and DNP-primed B cells that occurred after the administration of DNP-GL.     

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.     

The enhancement of humoral and cellular immune responses by dimethyldioctadecylammonium bromide

Dimethyldioctadecylammonium bromide (DDA) produced marked enhancement of both cellular and humoral immune responses to SRBC when administered to mice intraperitoneally, or of cellular immunity when given subcutaneously. Stimulated cellular responses were seen as increased footpad swelling as a measure of delayed hypersensitivity and increased antigen-induced blastogenesis. Elevation of humoral response was reflected in increased numbers of splenic plaque-forming cells (PFC) and in circulating anti-SRBC antibody. Adjuvancy did not depend on addition of the lipid of DDA to antigen, as both humoral and cellular responses were enhanced whether DDA and SRBC were admixed or injected separately 4 hr apart intraperitoneally. DDA also enhanced the PFC response to the T-cell independent antigen TNP-LPS. The DDA effects are accompanied by macrophage activation, which may mediate at least in part the observed responses. DDA-activated macrophages exhibit fast spreading, are highly phagocytic, and elaborate significantly greater amounts of thymocyte mitogenic factor(s) than do normal resident peritoneal macrophages. This activation may effect the stimulation of antigen-specific primary lymphocyte responses by adjuvant and expansion of memory-cell populations which lead to the observed enhancement of secondary responses.     

"Nonspecific" immunoenhancing T cells in tumor-bearing mice include anti-idiotypic subsets

Splenocytes from DBA/2 mice inoculated 3 wk earlier with syngeneic P815 mastocytoma tumor cells produce increased numbers of antibody plaque-forming cells (PFC) when stimulated with either sheep red blood cells (SRBC) or phosphorylcholine (PC) on Streptococcus pneumoniae R36a in vitro. The nature of this nonspecific hyperreactivity was investigated in mixed cultures of purified splenic T and B cells. The addition of T cells from P815 tumor-bearing mice (TP815) into the cultures of normal B cells produced a significant enhancement of the PFC response to both SRBC and PC, when compared with the effect of normal T cells added to control cultures. The idiotypic profile of the enhanced anti-PC response was studied by a PFC-inhibition assay with monoclonal antibodies against two distinct idiotopic determinants (Id) of the T15 family. Normal B cells produced greater than 90% of T15 Id-positive (Id+) PFC. Addition of normal T cells diminished the proportion of T15 Id+ PFC to approximately 60%, whereas the rest of PFC were Id-. Addition of the immunoenhancing TP815 cells into the normal B cells cultures elevated the number of both T15 Id+ and Id- PFC responses, proportionally. However, when TP815 cells were first incubated on T15 protein-coated dishes and the non-adherent fraction was added to B cell cultures, the anti-PC PFC response remained enhanced but consisted of predominently T15 Id- PFC. These observations suggest that the early stage of P815 tumor growth activates various populations of specific helper/amplifier T cells including subsets with anti-idiotypic activity and that the generalized increase of antibody response to various antigens in tumor-bearing mice may be regarded as a polyclonal activation of specific T cells.     

The enhancement of the immune response by pain stimulation in mice. I. The enhancement effect on PFC production via sympathetic nervous system in vivo and in vitro

Effects of catecholamines and osmotical and physical stimuli on the induction of anti-sheep red blood cells (SRBC) plaque-forming cells (PFC) were investigated in (C57BL/6 X BALB/c)F1 mice in vivo and in vitro. The anti-SRBC PFC from mice immunized with 5 X 10(7) SRBC was markedly increased by daily s.c. injections of epinephrine. The enhancement of PFC by epinephrine was completely blocked by preadministration with propranolol and hexamethonium, but not with phentolamine. The PFC was increased by osmotic and physical stimuli given once a day for 4 days after immunization with SRBC. The enhancement of PFC by these stimuli was completely blocked by preadministration with propranolol and hexamethonium. The enhancement of PFC by physical stimuli was observed in nonimmunized mice when spleen cells from stimulated mice were cultured with SRBC in vitro. In normal mice, the enhancement of PFC was observed 2 hr after one physical stimulation. However, spleen cells from mice given two physical stimuli did not show the enhancement of PFC after treatment with anti-Thy-1.2 antibody and complement, nor after removal of nonadherent cells. Next, the serum obtained from mice 30 to 60 min after a physical stimulation enhanced PFC of normal mice spleen cells in vitro, but the enhancement was abolished by the addition of propranolol. The enhancement of anti-SRBC PFC by s.c. injection of epinephrine suggested that the autonomic nervous system, especially the sympathetic nervous system, was activated by a local stimulus effect of the injection. This enhancement of anti-SRBC PFC appear to be due to the activation of antigen non-specific helper T lymphocytes by the beta-actin of endogenous catecholamines from the adrenal gland.     

Antibody formation in mouse bone marrow. II. Evidence for a memory-dependent phenomenon

Mouse bone marrow is barely capable of plaque-forming cell (PFC) activity in a primary response to sheep red blood cells (SRBC), while PFC activity in the secondary response to SRBC can be clearly demonstrated. This phenomenon was studied by means of cell transfer experiments.T cells, which are involved in an anti-SRBC PFC response, were shown to be very scarce in normal mouse bone marrow. This is considered to be the cause of the low PFC activity in the marrow during the primary response to SRBC.In normal mouse bone marrow precursors of IgM-PFC but not of IgG- and IgA-PFC could be found. Priming with SRBC induced the appearance of IgM-, IgG-, IgA- and T-memory cells in the marrow. These B- and T-memory cells were shown to be specific for the antigen which induced their appearance. It is thought that after a second injection of SRBC the IgM-, IgG- and IgA-memory cells can differentiate with the help of the T-memory cells within the bone marrow into IgM-, IgG- and IgA-PFC respectively.The sequence of appearance of the B-memory cells in the bone marrow was shown to be IgM-IgG-IgA.Six months after the intravenous injection of SRBC, the presence of B-memory cells could be demonstrated not only in spleen and bone marrow, but also in peripheral lymph nodes, mesenteric lymph node, Peyer's patches, thymus and blood. The increase in amount of B-memory cells was most prominent in the spleen.     

IgA responses in xid mice: oral antigen primes Peyer's patch cells for in vitro immune responses and secretory antibody production

Because the gut-associated lymphoreticular tissue (GALT), e.g., Peyer's patches (PP), of X-linked immunodeficient (xid) mice possesses a subpopulation of mature B cells, we have characterized the ability of xid mice to respond to the thymic-dependent antigen sheep erythrocytes (SRBC) given by the oral route. Gastric intubation of SRBC to xid (CBA/N X DBA/2) F1 male or CBA/N mice, followed by the in vitro culture of dissociated PP cells with SRBC, resulted in IgM, IgG1, IgG2, and high IgA anti-SRBC plaque-forming cell (PFC) responses. The addition of unprimed PP but not splenic T cells to splenic xid B cell cultures resulted in IgM anti-SRBC PFC responses, suggesting the importance of GALT T cells for support of the immune responses to SRBC by splenic B cells from xid mice. Furthermore, purified PP T cells from SRBC orally primed xid mice supported in vitro IgA anti-SRBC PFC responses in B cell cultures from either the PP or the spleens of nonprimed xid mice. Higher IgA responses, however, occurred in PP, when compared with splenic B cell cultures. Additional evidence that the GALT of xid mice contains functional IgA precursor cells was provided by the finding that cloned H-2k PP T helper cells (PP Th A) supported IgA responses in PP B cell cultures derived from (CBA/N X C3H/HeN) F1 male (xid) mice. On the other hand, splenic B cells from these xid mice, in the presence of PP Th A cells, did not support in vitro responses. These results suggest that unique subpopulations of T cells occur in the GALT of xid and normal mice; one T cell subpopulation may induce immature B cells to become precursor IgA cells in the PP. A separate GALT T cell subpopulation, e.g., isotype-specific helper T cells, effectively collaborates with mature IgA B cells for the induction of IgA responses to orally administered antigen. When xid mice were gastric intubated with SRBC, followed by i.p. injection of SRBC, good splenic IgA anti-SRBC PFC responses were seen. Salivary and serum IgA antibodies were also detected in these xid mice. Nevertheless, the magnitude of the anti-SRBC response in xid mice was lower than that seen in similarly treated normal mice. These studies indicate that the GALT of both xid and normal mice possess unique populations of T cells that support in vitro responses in xid B cell cultures from either the spleen or the PP, which direct the mature B cell populations present toward IgA isotype-specific responses.(ABSTRACT TRUNCATED AT 400 WORDS)     

Immune response of the Mongolian gerbil (Meriones unguiculatus) to sheep red blood cells.

The immune responses of Mongolian gerbils, Meriones unguiculatus, to sheep red blood cells (SRBC) were studied as compared to those of mice. After a single injection of SRBC, hemagglutinin titers in gerbils were significantly lower and hemolytic plaque-forming cells (PFC) in the spleen were less in number as compared to the response of mice. In gerbils the PFC response to a higher dose of bacterial lipopolysaccharide (LPS) was rather higher than in mice. The delayed-type hypersensitivity (DTH) assay on the foot-pad revealed that the responsiveness was considerably lower in gerbils than in mice.     

Genetic restrictions of transfer of delayed-type hypersensitivity to sheep erythrocytes: local versus systemic transfer.

Regulation of the transfer of delayed-type hypersensitivity (DTH) reactions to SRBC was studied using two assays. In the systemic transfer, SRBC immune cells were transferred intravenously and the recipient challenged by injecting antigen into the footpad. In the local transfer assay, SRBC immune cells were mixed with antigen before transfer into the footpad of the recipient. These studies utilized B10.D2 and B10.BR mice which are congenic strains differing only at H-2 region. DTH reactions can be transferred across H-2 barriers using a local transfer assay. When the immune cells were transferred intravenously or depleted of adherent cells prior to local transfer, DTH reactions cannot be transferred to an H-2 congenic recipient. Spleen cells from naive mice syngeneic to the intravenously transferred cells supply the necessary accessory cell when mixed with the antigen prior to injection into the footpad. This accessory cell may be a macrophage.     

Dose-dependent induction of immunologic enhancement and suppression after oral administration of antigen

The effects of feeding various quantities of a particulate antigen, sheep red blood cells (SRBC), on plaque-forming cells (PFC) in the spleen were determined. Mice were given various numbers of SRBC orally daily for 14 days, then injected with SRBC intravenously. Splenic IgA PFC responses to SRBC were enhanced in the mice fed 5 X 10(8) SRBC and splenic IgG PFC responses to SRBC were depressed in the mice fed 5 X 10(9) SRBC. Adoptive transfer experiments showed that enhancement of splenic IgA PFC responses and suppression of splenic IgG PFC responses were induced by the T-cell rich fraction from Peyer's patches (PP) and the spleen in 5 X 10(8) SRBC- and 5 X 10(9) SRBC-fed mice, respectively. Kinetic studies revealed that IgA helper cells or IgG suppressor cells appeared in PP 2 days after oral administration and 4 days after it in the spleen.     

Formation of heterophile antibodies by human tonsilar lymphocytes: II. In vitro stimulation with allogeneic cells

Short-term cultures of human tonsilar lymphocytes (HTL), 5 × 10⁶ cells/culture, in medium RPMI 1640 supplemented with human group AB serum were studied for the production of plaque-forming cells (PFC) against sheep (SRBC) and bovine (BRBC) red blood cells following in vitro stimulation by various allogeneic lymphoid cells. Of 55 HTL specimens examined, 48 produced a significant number (50–300/culture) of PFC against SRBC and/or BRBC following the in vitro stimulation. The optimal doses of the stimulator HTL and peripheral blood lymphocytes (PBL) were 10⁷ and 5 × 10⁶/culture, respectively. After the stimulation, PFC appeared in significant numbers on the third day, reached the peak number on the sixth day, and decreased sharply in number thereafter. Removal of E-rosetting cells from both stimulator and responder populations abolished the PFC formation. PFC formation against SRBC was inhibited by solubilized Forssman antigen, while PFC formation against BRBC was inhibited strongly by Hanganutziu-Deicher antigen, hardly by Paul-Bunnell antigen and not at all by Forssman antigen. Supernatants of mixed lymphocyte culture of PBL were shown to enhance PFC formation of HTL cultures stimulated by allogeneic lymphocytes. The results of this study indicated that in vivo primed B cells of the HTL were triggered in vitro by allogeneic stimulation for the heterophile antibody formation. Since these antibodies are apparently directed against Forssman and Hanganutziu-Deicher antigens, the “allo” nature of these antigens as well as their relationship to the previously described heterophile transplantation antigens have to be clarified.     

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.     

Fumonisin B1 alters sphingolipid metabolism and immune function in BALB/c mice: Immunological responses to fumonisin B1

Fumonisins have been reported to have diverse effects on animals, including immunosuppression in chickens and feeder calves; therefore, the effects of fumonisin B₁ (FB₁) on immune function in BALB/c mice was investigated. When administered i.p. with sheep red blood cells (SRBC), 5 to 100 µg of FB₁ reduced the number of plaque-forming cells (PFC) produced against SRBC; however, when administered daily, 1 to 50 µg of FB₁ caused a 4 to 12-fold increase in the number of PFC after SRBC injection. Therefore, FB₁ is not only immunosuppressive; but also, immunostimulatory. To test the possibility that there may have been an immune response to FB₁ as an antigen, FB₁ was injected into mice and the number of splenic cells forming rosettes on FB₁-treated SRBC was determined. There were dose-dependent increases in the antigen-binding cells, with up to 4.9- and 4.6-fold increases, respectively, upon primary and secondary immunization. FB₁-binding immunoglobulins could be detected in sera from some treated mice, but this response was not obtained in every experiment. In summary, these results show that FB₁ has diverse effects on the immune system, causing both stimulation and suppression of the response to foreign antigens, and apparently inducing an antigenic response to FB₁.Abbreviations DMEM Dulbecco's Modified Eagle's Medium - FB₁ fumonisin B₁ - FCS fetal calf serum - PBS phosphate buffered saline - PFC plaque forming cells - RFC rosette forming cells - SRBC sheep red blood cells