Population kinetics of peritoneal LPS-reactive B lymphocytes

The dynamic behaviour of isolated populations of peritoneal LPS-reactive (LPSr) B lymphocytes was studied upon transfer of peritoneal cells (PerC) from C57BL/6 LPS responder into C57BL/10ScCr LPS non-responder mice. We have followed the persistence and life-span of the transferred LPSr donor B cells in the spleen and peritoneal cavity of both intact and X-irradiated adult hosts after i.v. or i.p injection and neonatal 1-day-old recipients after i.v. transfer. We have found that lymphocyte life-spans can be influenced by local host environments, as the transferred PerC LPSr cells showed different kinetics according to their route of injection, organ localization, and age or state of the recipients. Thus, while in intact hosts most of the transferred peritoneal LPSr cells decayed with time, following transfer into X-irradiated recipients the same cells were able to expand and replenish the lymphoid tissues of the host. Moreover, upon transfer into intact hosts, the kinetic properties of peritoneal LPSr cells from adult mice differ from splenic LPSr cells of age-matched animals, but mimic those of spleen cells from young, 1-to 2-week-old donors. These findings may reflect the different phenotype composition of adult spleen cells (poor in Ly1 B cells) and peritoneal and neonatal spleen cells (both rich for Ly1 B cells), or may be the result of selective events leading to the peritoneal accumulation of cells with different population dynamics.     

Early B cell precursors in long-term bone marrow culture: selective development in the bone marrow of irradiated recipients

The primary site for the growth and differentiation of B cell precursors in irradiated recipient mice was investigated. Bone marrow (BM) cells from lipopolysaccharide (LPS)-responder C57BL/6 mice were transferred into irradiated LPS-nonresponder C57BL/10ScCr mice, and the generation of donor-derived B cells in the recipient was monitored by determining the immunoglobulin-producing cells developed in the LPS-stimulated cultures of recipient's spleen cells as well as BM cells. As previously stated, the transfer of fresh BM cells resulted in the development of LPS-reactive cells both in spleen and BM simultaneously. On the other hand, when long-term cultured BM cells which were shown to be devoid of B cells and pre-B cells were used as the donor cells, the development of LPS-reactive cells was first observed only in BM, and subsequently in both BM and spleen. The failure to detect LPS-reactive cells in the spleen in the early phase, or day 11 after irradiation and reconstitution, was not attributed to the culture condition or the existence of suppressive activity in day 11 spleen cells. These results indicate that B cell precursors lodge only in the BM of irradiated recipients, grow and differentiate in the same place, and then the differentiated progeny migrate to peripheral lymphoid organs.     

Clonal persistence of B lymphocytes in normal mice is determined by variable region-dependent selection

Many adult splenic B cells die within 1 week in the spleen of adoptive adult recipient mice; in contrast, the cellular environment of newborn recipients allows for their expansion and persistence for several weeks. In the present study, we show that the local environment of adult peritoneal cavity also allows adult splenic B cells to persist for over 2 weeks after intraperitoneal transfer. In order to determine whether the persistence of donor B cells in newborn hosts and in the peritoneum of adult recipients results from a selection process involving the clonal specificities expressed, the variation in time of VH gene family repertoires of donor B cells was analyzed in the hosts. At different times after the transfer of splenic cells from lipopolysaccharide (LPS)-reactive mice into LPS-non responder histocompatible recipients, mRNA colony blot assays were performed. The results show that among the donor adult LPS-reactive B cells, the VH genes are differently used by the expanding or persisting B cells, in both kinds of recipients. Thus, cells expressing J558 or VH11 gene families are, in particular, positively selected, while those expressing D-proximal or J606 and 36-30 VH gene families are less selected. These findings demonstrate that the propensity of B cells to persist and expand is determined by their selection through their immunoglobulin variable regions, rather than by genetic properties linked to particular B cell subsets.     

Quantitative analysis of the chimæric state in mice: II. Cytological examination of the proportion of proliferating donor and host cells in runt disease in mice

The distribution of donor cells in the lymphoid organs of mice suffering from acute runt disease was investigated by means of the cytological marker (T6). In all the strain combinations studied relatively low proportions of donor cells were identified in the spleen and bone marrow. In the A→CBA-T6T6 and C57BL→CBA-T6T6 combinations high proportions of donor cells were found in the lymph nodes and thymus. Few donor cells at all lymphoid sites were identified in the CBA-T6T6→C57BL combination, though the recipients showed unquestionable clinico-pathological signs of runt disease.

Despite marked splenomegaly in 12-day-old runts, the mean total number of cells in the spleen was similar to that in normal mice and mice injected at birth with isologous cells. In the A→CBA-T6T6 and C57BL→CBA-T6T6 combinations donor cells significantly contributed to the total cellularity of the enlarged spleen, in contrast to the CBA-T6T6→C57BL combination in which the host's spleen consisted almost exclusively of host cells.

Grafting tests showed that runted mice can be either non-specifically or specifically tolerant which seemed to depend on the degree of lymphoid atrophy and the degree of chimerism. Some of the animals that eventually rejected skin grafts from spleen inoculum donors, continued to be chimeric for donor lymphoid cells.

A mechanism for runt disease could be mutual interaction between donor and host cell populations causing reduction of the host's lymphoid reserve and consequent appearance of clinical symptoms of disease.

     

Comparative Mucigenic Responses of T-Cells and B-Cells in Spleens of Mice of Varying Age

Mouse spleen cell mitogenic responses to Phytohemagglutmin (PHA), conconavalin A (con A), staphylococcal enterotoxin B (SEB) and lipopolysaccharide (LPS) were studied as a function of age. In CD-1 mice, spleen cell DNA synthesis in response to stimulation by PHA, con A and SEB varied from 181 - 33% of adult values for the first 3 weeks of life. By 6 weeks, the PHA response was 63% of the adult response and achieved adult values by 8 weeks of life. In contrast to these T-cell responses, DNA spleen cell synthesis in response to LPS was approximately that of adults as early as 7 days after birth. When spleen cell mitogenic responses were studied in C57B1/6J mice a similar pattern emerged. C57 spleen cell responses to PHA, con A and SEB varied from 241 - 54% of adult values for the first 3 weeks of life. By 4 weeks, spleen cell responses to PHA and con A were approximately those of adults. Again, C57 spleen cell responses to LPS were equivalent to adult values as early as 7 days after birth.     

The Polyclonal Lipopolysaccharide Response Is Accessory-Cell-Dependent

Different concentrations of spleen cells from C57BL.10 mice were activated with lipopolysaccharide (LPS), and DNA synthesis and IgM and IgG secretion were measured. The dilution curve was sigmoid, and the response was rapidly lost below a certain cell concentration. In the presence of thymocytes or spleen cells from the LPS-non-responder strain C57BL.10/ScCr the dilution curve for the LPS response of cells from C57BL.10 mice became linear, and the overall response was increased. Irradiated cells could not restore the response at suboptimal cell concentrations. In addition, enriched T cells restored the response as well as normal spleen cells, whereas enriched B cells did not. We compared the restoring capacity of different filler cells for the LPS response with that of a plasmacytoma cell line cultured at suboptimal cell concentrations. The results are compatible with the idea that the filler cells provide growth-stimulating activity to LPS-responsive cells but growth-supporting activity to the tumour cells. Furthermore, highly enriched B-cell populations respond poorly to LPS, but the response can be partly restored by filler cells. These data suggest that the LPS response is accessory-cell-dependent.     

Genetic regulation of lipopolysaccharide responses in NZB mice

Several of the autoimmune defects of NZB mice have been linked to chromosome 4 where the Lps gene which regulates B cell activation by bacterial lipopolysaccharide (LPS) is found. Thus, studies of an NZB.Lpsd strain may facilitate functional analysis of B cell hyperactivity. To develop NZB.Lpsd mice, the Lpsd mutation of C57BL/10ScN mice was further characterized by studying the influence of Lpsd on LPS-induced spleen cell proliferation colony-stimulating factor (CSF) production, and B cell colony-forming unit (CFU-B) proliferation in (C57BL/10SnJ X C57BL/10ScN) F1 X C57BL/10ScN mice. Twenty-one of 27 backcross offspring demonstrated concordance of results in the three assays indicating common genetic regulation of these traits. Subsequently, the Lps allele of NZB mice was characterized by determining the mitogen responsiveness, CSF production and CFU-B proliferation of (NZB X C57BL/10ScN) F1 X C57BL/10ScN mice. In addition, concordance of assortment of the C57BL/10ScN Mupb allele and LPS unresponsiveness was verified. Results of these assays were concordant in 12 of 14 backcross mice, indicating that NZB LPS responsiveness is also regulated by a gene or closely linked set of genes on chromosome 4. Further, the LPS responsiveness of homozygous fifth backcross NZB.Lpsd mice was significantly diminished compared to that of NZB mice. Interestingly, the hypergammaglobulinemia and anti-DNA antibody levels in 6-month-old Lpsd mice did not differ from those of NZB mice despite the absence of LPS-responsive CFU-B.     

Deficient growth of C57BL marrow cells transplanted in F1 hybrid mice: Association with the histocompatibility-2 locus

The ability of C57BL, C3H, and A strain marrow cells to proliferate on transplantation into irradiated isogenic, F₁ hybrid, and backcross progeny mice has been investigated by the spleen-colony technique and by measuring the newly-formed DNA in the recipient spleen with [¹³¹I] 5-iododeoxyuridine. Transplants of C57BL cells grew poorly in (A×C57BL)F₁ and in (C57BL×C3H)F₁ and reciprocal hybrids, as compared with isogenic and allogeneic hosts, whereas C3H and A strain marrow grafts were successful in isogenic, F₁ hybrid and backcross recipients. In segregating backcross progeny, i.e. in offspring from F₁ hybrid females mated to C57BL males, the frequency of success or failure of the C57BL grafts suggested that the trait was controlled by a single pair of genetic determinants at an autosomal locus. The latter is apparently linked with, or part of, the H-2 region in the IXth linkage group. The experimental evidence suggested also that the failure of C57BL haemopoietic cell grafts in H-2 heterozygotes was not related to exhaustion of donor cells by excess of recipient isoantigen but rather to lack of expression in the heterozygotes of histocompatibility-related growth requirements yet undefined. These requirements are specific for haemopoietic cells, but not for skin grafts, and resulted most probably from the effect of genetic (inter-allelic) interaction involving H-2 or an H-2-linked locus.     

Pathological changes in F1 hybrid mice following transplantation of spleen cells from donors of the parental strains

It has already been reported by one of us (Boyse, 1959) that intraperitoneal transplants of spleen cells from A strain donor mice that had been immunized against C57BL strain tissues were invariably lethal to hosts of the F₁ (C57BL×A) constitution.

In this report an account is given of the pathological changes in F₁ hybrid hosts that have received intravenous or intraperitoneal transplants of spleen cells from parental strain donors, with particular reference to lethal transplants. Here the outstanding features are splenomegaly, wasting, progressive histiocytosis in the spleen and lymph nodes, disappearance of lymphoid tissue, focal necrosis of the spleen and cellular infiltrations round the hepatic vessels. Following transplantation by the intraperitoneal route there are also severe pancreatic lesions associated with fat necrosis and ascites.

Differential (donor/host) cell counts of host spleen cell suspensions indicate that the spleen may be virtually replaced by donor cells, the majority of which are histiocytes. Erythropoietic function is progressively supplanted by donor tissue.

Similar, but reversible and less extensive changes occur with other (non-lethal) donor/F₁-host combinations. These hosts do not waste and the proportion of donor cells included in the host spleens falls until their detection, by present methods, is no longer possible.

     

Chimerism but not neonatal antigen exposure induces transplant tolerance

Acquired transplant tolerance could be readily induced during foetal or neonatal period through donor cell infusion, but it is not the case in adults. This phenomenon has been attributed to the variation of immune system development in neonatal and adult periods. To investigate the role of immature immune system and chimerism in neonatal transplant tolerance, irradiated spleen cells or cell fraction from F1 (BALB/c × C57BL/6) or GFP-F1 mice were injected intravenously into neonatal C57BL/6 mice to induce tolerance. Irradiated cells or cell fraction could not induce chimerism and transplant tolerance in neonatal mice, even increasing the dose of donor cells to 5 × 10(7). Living donor cells induced tolerance in neonatal mice, and the quantity of living cells was correlated with the degree of chimerism and tolerance. At the amount of 3 × 10(7) F1 spleen cells, skin grafts were survived permanently in more than 80% of treated mice. However, the amount of 0.7 × 10(7) F1 spleen cells could only slightly prolong allografts' survival. The more donor cells were infused, the higher level of chimerism was achieved, and the higher frequency of alloreactive T cells was deleted. Chimerism is prerequisite for the induction and maintenance of tolerance. Chimerism in long-term tolerant mice was significantly higher than that in chronic graft rejected mice, with 6.48 ± 4.02% versus 1.41 ± 0.77%. It implies that transplant tolerance depends on the establishment of chimerism, but not on antigen exposure to immature immune system in foetus or neonates.     

Completely allogeneic spleen cells induced cytolytic neonatal tolerance to alloantigens,but failed to establish allo-helper interactions with host T cells.

The injection of spleen cells from F1 mice into-newborns from a parental strain results in the establishment of cytolytic tolerance to donor alloantigens and the development of a lupus-like disease. This syndrome is the consequence of the recognition by alloreactive host CD4+ T cells of discordant major histocompatibility complex (MHC) class II antigens on semi-allogeneic donor B cells. We have analysed whether completely allogeneic spleen cells are as able as semi-allogeneic spleen cells to induce cytolytic tolerance to donor alloantigens and to co-operate with alloreactive T cells for autoantibody production. BALB/c mice were injected at birth with Thy-1-depleted spleen cells from (C57BL/6 x BALB/c)F1 or C57BL/6 mice, either alone or in combination. Cytolytic tolerance was always induced, as manifested by persistence of chimerism and acceptance of skin allografts. However, only F1 semi-allogeneic B cells were activated by alloreactive host T cells to produce anti-DNA IgG antibody. The deficient co-operation between BALB/c CD4+ T cells and completely allogeneic C57BL/6 B cells was confirmed after neonatal injection of (C57BL/ 6 x BALB/c)F1(Igha) spleen cells together with C57BL/6(Ighb) spleen cells. These mice developed anti-DNA antibodies bearing only the Igha allotype. Similar results were observed in experiments of allogeneic interaction in vitro, in which BALB/c CD4+ T cells were cocultured with either (C57BL/6 x BALB/c)F1 or C57BL/6 B cells. The present results demonstrate that completely allogeneic spleen cells efficiently induced cytolytic unresponsiveness to donor alloantigens, but B cells contained in this spleen cell population were unable to establish allo-helper interactions with alloreactive CD4+ T cells, suggesting that cytolytic and helper T-cell interactions involved in alloreactivity may be different.     

Lipopolysaccharides from Bacteroides fragilis are mitogenic for spleen cells from endotoxin responder and nonresponder mice.

The lipopolysaccharides (LPS) from Bacteroides fragilis are structurally atypical and give weak responses in most tests of endotoxic activity, but the mitogenic activity of LPS from B. fragilis has not been tested. We prepared LPS from B. fragilis 23745 by three methods and compared their mitogenic activity for murine spleen cells with that of LPS from Escherichia coli K235 prepared by similar techniques. LPS extracted from B. fragilis with hot phenol-water, with butanol-water, or by detergent separation from the outer membrane were mitogenic for spleen cells from C57BL/10ScN, C57BL/10ScCR, and C3H/HeJ mice. The outer membrane, the outer membrane protein-polysaccharide complex, and the capsular polysaccharide from B. fragilis were also mitogenic for spleen cells from the same murine strains. LPS extracted from E. coli K235 with hot phenol-water, butanol-water, or sodium deoxycholate were mitogenic for C57BL/10ScN spleen cells, but only the LPS extracted with butanol and deoxycholate were stimulatory for spleen cells from C57BL/10ScCR and C3H/HeJ mice. Two types of LPS varying in the 2-keto-3-deoxyoctonate-to-carbohydrate ratio were isolated from E. coli K235 with sodium deoxycholate; both endotoxins contained protein which was typical of lipid A or endotoxin protein. These results indicate that the LPS from B. fragilis is a potent mitogen for spleen cells from endotoxin responder and endotoxin nonresponder mice.     

Gamma interferon production in endotoxin-responder and -nonresponder mice during infection.

The production of gamma interferon (IFN-gamma) in response to infection and to a number of other agents was compared in Lpsn (C3H/HeN and C57BL/10ScSn) and Lpsd (C3H/HeJ and C57BL/10ScCr) mouse strains. Large differences in IFN-gamma production were observed between C57BL/10ScCr mice and the other mouse strains. With the exception of C57BL/10ScCr, all mouse strains, including C3H/HeJ, exhibited transient levels of IFN-gamma during infection with Salmonella typhimurium. Spleen cells of these mice, explanted on day 3 of infection, produced in vitro IFN-gamma spontaneously; this production was enhanced considerably by heat-killed S. typhimurium, heat-killed Propionibacterium acnes, concanavalin A (ConA), or lipopolysaccharide (LPS). These stimuli, except for LPS, also induced IFN-gamma production in cultures of normal spleen cells from noninfected animals. In contrast, C57BL/10ScCr mice produced no IFN-gamma following infection with S. typhimurium. Also, spleen cells of these mice, explanted on day 3 of infection, exhibited no spontaneous IFN-gamma production. A marginal response was obtained by additional stimulation of the cells with killed S. typhimurium, and a moderate response was obtained with ConA. Normal spleen cells from noninfected C57BL/10ScCr mice showed no IFN-gamma response to killed S. typhimurium, killed P. acnes, or LPS and only a low response to ConA. Impaired IFN-gamma production in C57BL/10ScCr mice was also evident during infection with Plasmodium chabaudi chabaudi, with which a low IFN-gamma response was seen only occasionally. Also, spleen cells from infected animals (days 2 to 8 after infection) exhibited only a very low level of IFN-gamma production in vitro; however, this production could be enhanced further by ConA. In comparison, C57BL/10ScSn mice infected with P. chabaudi chabaudi produced significant amounts of IFN-gamma. Spleen cells explanted from infected animals produced IFN-gamma spontaneously in vitro; this production was enhanced further by killed P. acnes and ConA. The results showed that in addition to the defect in LPS responsiveness, C57BL/10ScCr mice possess a defect in IFN-gamma production in response to different stimuli. During infection, IFN-gamma production and sensitization to LPS occurred in parallel. Infected Lpsn mice exhibited enhanced sensitivity and infected Lpsd C3H/HeJ mice exhibited reasonable sensitivity to the lethal effects of LPS. Lpsd C57BL/10ScCr mice remained resistant to LPS when infected with S. typhimurium and exhibited only marginal sensitivity when infected with P. chabaudi chabaudi.     

Life-long tolerance and chimerism in parental mice induced with F 1 hybrid cells

We have induced specific immunological tolerance towards (C57BL × CBA-T6T6) F₁ skin grafts in newborn recipients of the parental CBA strain by one injection of 20 × 10⁶ or 40 × 10⁶ F₁ spleen cells. Approximately 80 % of the CBA recipients were highly tolerant (the grafts survived for more than 50 days). Many of the highly tolerant mice retained fully preserved grafts until natural death. The highly tolerant CBA mice had dividing (C57BL × CBA-T6T6) F₁ cells in their spleen (12–13 %) and lymph nodes (12–15 %). The proportion of these cells decreased with time, but we found a few of them even at 567 days of life (0.7 and 4.2 %, respectively). We have concluded that specific immunological tolerance to tissue grafts induced at birth can last throughout the entire life-span of a mouse. The tolerance persists in spite of a very low proportion of dividing donor cells within the lymphoid tissue of tolerant hosts.     

Host conditioning with total lymphoid irradiation and antithymocyte globulin prevents graft-versus-host disease: the role of CD1-reactive natural killer T cells.

Our previous studies in mice showed that the nonmyeloablative conditioning regimen of fractionated irradiation of the lymphoid tissues (total lymphoid irradiation; TLI) and depletive anti-T-cell antibodies (anti-thymocyte serum) markedly increased the percentage of regulatory DX5+ and natural killer 1.1+ T cells in the mouse spleen, and prevented acute lethal graft-versus-host disease (GVHD) in BALB/c mice (H-2(d)) following the transplantation of bone marrow (BM) and peripheral blood mononuclear cells (PBMC) from C57BL/6 (H-2(b)) donors. The object of the current study was to determine whether the TLI and anti-thymocyte serum regimen protected natural killer T-cell deficient CD1(-/-) BALB/c mice against GVHD after BM and PBMC transplantation from C57BL/6 donors, and whether a similar conditioning regimen of TLI and anti-thymocyte globulin (ATG) can prevent GVHD in Lewis rat (RT1(l)) hosts after BM and PBMC transplantation from ACI rat (RT1(a)) donors. The experimental results in mice showed that, although wild-type BALB/c hosts are protected in association with a marked increase in CD1- reactive T cells expressing the invariant TCR identified with a CD1 tetramer reagent; CD1(-/-) BALB/c hosts are not. Studies of chimeric donor cells in mice protected from GVHD showed donor T-cell polarization to a Th2 cytokine pattern. Results in rats showed that approximately 1000 fold more donor PBMC cells were required to induce a similar incidence of lethal GVHD in TLI and ATG conditioned hosts as compared with hosts conditioned with single-dose total-body irradiation or total-body irradiation and ATG. Surviving TLI and ATG conditioned rat hosts were complete chimeras. In conclusion, the TLI and ATG/anti-thymocyte serum conditioning regimen protects against GVHD in rats and mice, and regulatory natural killer T cells are required for protection.     

Effect of adrenalectomy on donors and recipients on repopulation of parental lymphocytes in first generation hybrids

Lymph gland cells from sensitized and normal CBA/HT6T6 mice were injected into F₁(CBA/HT6T6×C57BL/6) mice subjected to bilateral adrenalectomy 7 days before injection of the donor cells. In one of the experiments both adrenals were removed from the donors four weeks before the lymph gland cells were taken. Adrenalectomy on the recipients led to an increase in the percentage of donor mitoses in the spleen at all times of transfer, provided that the lymphocytes were taken from sensitized donors, whereas the number of donor mitoses in the lymph glands was indistinguishable from that in the control groups. An increase in the percentage of donor mitoses in the spleen of the adrenalectomized mice was observed only on the 5th day after transfer if lymphocytes from unsensitized donors were used; on the first day after injection of the cells an increase in mitotic activity of the donor cells in the lymph glands was observed. If the lymphocytes were taken from adrenalectomized and sensitized donors, the injected cells retained their power of increased mitotic activity in the spleen of the irradiated recipient on the first day after injection.     

Progressive Accumulation of Bacterial Lipopolysaccharide In Vivo During Murine Acute Graft-Versus-Host Disease

In a previous report the authors demonstrated that acute graft-versus-host disease (GVHD) was associated with pathologic amounts of tumour necrosis factor alpha (TNF-α) and the appearance of lipopolysaccharide (LPS) in the blood of GVH reactive mice just prior to death. In this study the authors have investigated the kinetics of LPS accumulation in different organs during the course of acute GVHD using a murine model. Unirradiated C57BL/6×AF1 (B6AF₁) mice were transplanted with C57BL/6 (B6) lymphoid cells and killed at predetermined times after transplantation for LPS analysis. Control animals were injected with either 60×10⁶ B6AF1 lymphoid cells (syngeneic) or 60×10⁶ irradiated (2000 rad) CBA lymphoid cells (allogeneic). Lipopolysaccharide began to appear in the liver and the spleen of GVH reactive mice from day 2 post-transplant and by day 10 all GVH reactive mice tested positive for hepatic and splenic LPS. Low levels of LPS were detected in some control mice from days 2 to 10 post-transplant but LPS was never detected after day 10 in control groups. Total hepatic and splenic LPS in acute GVH reactive mice peaked at a time coincident with the appearance of LPS in the serum and with the onset of mortality. These results demonstrate that tissue levels of LPS increase throughout the course of acute GVHD and are sufficient to trigger the release of pathologic amounts of TNF-α from primed macrophages resulting in the cachexia and mortality associated with acute GVHD in this model.     

Is the follicular dendritic cell a primarily stationary cell?

The cell nature of follicular dendritic cells (FDC), a member of dendritic cell group, was examined to see whether or not they are recirculating cells on splenic implantation study. Slices of BALB/c mouse spleen were implanted into C57BL/6 mice neonatally thymectomized and reconstructed by F1 (BALB/c x C57BL/6) thymus grafting. On H-2 class I immunohistology 6 months later, host spleens consisted of only the cells including FDC of host (C57BL/6) type. On the other hand, FDC of regenerated splenic grafts were of splenic donor (BALB/c) origin and haematogenic cells including germinal centre lymphocytes were of the host (C57BL/6) origin. The fact that the FDC in the regenerated splenic grafts reside irrespective of the replacement by host recirculating cells indicates that FDC belong primarily to stationary cell populations but not recirculating cell populations.     

The effect of an immunoglobulin mu transgene on B cell maturation.

In mu 17.2.25-transgenic (M54) mice the absolute number of surface IgM (sIgM) B cells in lymphoid organs is drastically reduced compared to normal C57BL/6 mice and a high frequency of B cells express the immunoglobulin (Ig) encoded by the transgene rather than endogenous Ig on the surface. To determine the effect of a mu transgene on B cell development, adoptive cell transfers were performed using mu transgenic (M54) bone marrow and fetal liver cells. The data presented support the following conclusions: (a) adult transgenic bone marrow contains functional B cell precursors able to mature and repopulate the spleen and peritoneum of recipient mice. The relative frequency of transgene (sIgMa) and endogenous (sIgMb) surface sIgM-positive B cells reconstituted by transgenic bone marrow in allotype-matched C57BL/6 recipients is the same as in the M54 donors; (b) serum analysis indicates that transgenic bone marrow donor cells can reconstitute B cells in congenic and severe combined immunodeficient (SCID) recipient mice; (c) transgenic fetal liver cells are not a richer source of precursors for B cells expressing endogeneous Ig; (d) in transgenic mice sIgM+ B cells are not restricted to the CD5+ phenotype, however, the relative frequency of sIgMb B cells that are CD5+ is higher in transgenic than normal mice; and (e) bone marrow cells from adult normal and transgenic mice are able to generate CD5+ B lymphocytes in the spleen and peritoneum of allotype-congenic and neonatal SCID recipient mice. The results indicate that the presence of a complete mu heavy chain transgene does not result in a selective developmental block of "conventional" bone marrow-derived pre-B and B cells.     

L-Selectin-deficient SJL and C57BL/6 mice are not resistant to experimental autoimmune encephalomyelitis

L-selectin has been suggested to play a role in the pathogenesis of experimental autoimmune encephalomyelitis (EAE), an animal model of multiple sclerosis. Here we demonstrate that L-selectin(-/-) SJL mice are susceptible to proteolipid protein (PLP)-induced EAE because the compromised antigen-specific T cell proliferation in peripheral lymph nodes is fully compensated by the T cell response raised in their spleen. Transfer of PLP-specific T cells into syngeneic recipients induced EAE independent of the presence or absence of L-selectin on PLP-specific T cells or in the recipient. Leukocyte infiltration into the central nervous system parenchyma was detectable independent of the mode of disease induction and the presence or absence of L-selectin. In addition, we found L-selectin(-/-) C57BL/6 mice to be susceptible to myelin oligodendrocyte glycoprotein-induced EAE. Taken together, we demonstrate that in SJL and C57BL/6 mice L-selectin is not required for EAE pathogenesis. The apparent discrepancy of our present observation to previous findings, demonstrating a role of L-selectin in EAE pathogenesis in C57BL/6 mice or myelin-basic protein (MBP)-specific TCR-transgenic B10.PL mice, may be attributed to background genes rather than L-selectin and to a unique role of L-selectin in EAE pathogenesis in MBP-TCR-transgenic mice.