Thoracic Duct Cells Research Articles

Митотическая активность клеток грудного протока кроликов связана с возрастом и абсолютным количеством лимфоцитов

Митотическая активность клеток грудного протока кроликов связана с возрастом и абсолютным количеством лимфоцитов

Efficacy and mechanisms of action of vitamin D in experimental polyarthritis

Vitamin D (vit D) status has been linked to the occurrence and severity of auto-immune and inflammatory diseases. This study evaluates the effects of vit D status on adoptive transfer of adjuvant-induced arthritis (ATA). Rats maintained on diets replete or deficient in vit D3 received arthritogenic thoracic duct cells and were monitored for severity of arthritis. CD45(+) cells obtained by collagenase digestion of hind-paw synovium-rich tissues (SRTs) were analysed to observe the effects of dietary vit D3 on the inflammatory process. Arthritis was more severe in vitamin D-deficient (vit-D(-)) rats compared with vitamin D-replete (vit-D(+)) rats. Resolution was delayed in vit-D(-) rats compared with vit-D(+) rats, or rats fed standard chow. During the acute phase of ATA, numbers of CD45(+) cells were significantly increased in the SRTs of vit-D(-) rats compared with vit-D(+) rats. This increase involved T-cells, polymorphonuclear leukocytes, macrophages, dendritic cells (DCs) and MHC II(hi) cells that resemble activated monocytes. A major difference between the dietary groups was that most DCs at the peak of inflammation in vit-D(-) rats were CD4(-), whereas in convalescent vit-D(+) rats most expressed CD4. Multiple categories of genes expressed by DCs differed between deficient and replete rats, with deficiency being associated with relative upregulation of certain pro-inflammatory genes and replete status being associated with upregulation of genes associated with resolution of inflammation. The findings indicate that ATA is more severe and prolonged in vit-D deficiency, that vit-D deficiency promotes accumulation of CD4(-) DCs in synovium during ATA and that a gene-expression profile is likely to contribute to the observed increased severity and duration of arthritis.

Recruitment of dendritic cells and macrophages during T cell-mediated synovial inflammation

Adoptive transfer of adjuvant-induced arthritis was used in this study to examine local macrophages and dendritic cells (DCs) during T cell-mediated synovial inflammation. We studied the influx of CD11b+CD11c+ putative myeloid DCs and other non-lymphoid CD45+ cells into synovium-rich tissues (SRTs) of the affected hind paws in response to a pulse of autoreactive thoracic duct cells. Cells were prepared from the SRTs using a collagenase perfusion-digestion technique, thus allowing enumeration and phenotypic analysis by flow cytometry. Numbers of CD45+ cells increased during the first 6 days, with increases in CD45+MHC (major histocompatibility complex) II+ monocyte-like cells from as early as day 3 after transfer. In contrast, typical MHC II- monocytes, mainly of the CD4- subset, did not increase until 12 to 14 days after cell transfer, coinciding with the main influx of polymorphonuclear cells. By day 14, CD45+MHC IIhi cells constituted approximately half of all CD45+ cells in SRT. Most of the MHC IIhi cells expressed CD11c and CD11b and represented putative myeloid DCs, whereas only approximately 20% were CD163+ macrophages. Less than 5% of the MHC IIhi cells in inflamed SRT were CD11b-, setting a maximum for any influx of plasmacytoid DCs. Of the putative myeloid DCs, a third expressed CD4 and both the CD4+ and the CD4- subsets expressed the co-stimulatory molecule CD172a. Early accumulation of MHC IIhiCD11c+ monocyte-like cells during the early phase of T cell-mediated inflammation, relative to typical MHC II- blood monocytes, suggests that recruited monocytes differentiate rapidly toward the DC lineage at this stage in the disease process. However, it is possible also that the MHC IIhiCD11c+ cells originate from a specific subset of DC-like circulating mononuclear cells.

Immune regulation in adjuvant-induced arthritis: possible implications for innovative therapeutic strategies in arthritis.

Adjuvant-induced arthritis (AIA), the first experimental arthritis model, was described in 1956 (1,2), at a time when experimental autoimmune diseases affecting the central nervous system, peripheral nervous system, thyroid, and eye had been described, and autoimmunity began to be considered a significant mechanism in the pathogenesis of organ-specific inflammatory disease (3,4). AIA, which appeared in rats immunized with Mycobacterium tuberculosis in oil, showed suggestive similarities in clinical onset and course, as well as the pattern of lesions in joints, skin, eye, and mucosae, to reactive arthritis associated with infection by enteric organisms (primarily gram-negative bacilli) (for review, see ref. 5). The intensified, precocious appearance of AIA lesions at joint or skin sites traumatized by various means suggested that the disease might represent a disseminated autoimmune response to a joint or connective tissue antigen (6). Indeed, AIA could be transmitted by transferring sensitized lymph node cells (7,8) or thoracic duct cells (9) from sensitized donors to normal recipients, without administering M tuberculosis to the latter group.

Characterization of thoracic duct cells that transfer polyarthritis.

Polyarthritis may result from the haematogenous distribution of arthritogenic effector lymphocytes that emerge in the efferent lymph and pass through the thoracic duct (TD) to the circulation. We therefore examined whether TD cells collected from rats in the late prodrome of adjuvant-induced arthritis (AA) could transfer polyarthritis adoptively and whether these cells included a subpopulation of arthritogenic cells that could be identified phenotypically. Unfractionated TD cells collected from donor rats 9 days after adjuvant inoculation were injected intravenously into normal syngeneic recipients in numbers equivalent to the overnight harvest from a single donor. TD cell subpopulations, equivalent in number to proportions in the same inoculum, were prepared by negative selection. Unfractionated TD cells transferred polyarthritis without in vitro stimulation or conditioning of recipient animals. Abrogation of arthritogenicity by depletion of alpha/beta TCR(+) cells showed that the polyarthritis was transferred by T cells. Negatively selected CD4(+) but not CD8(+) TD cells transferred AA. An arthritogenic subpopulation of CD4(+) T cells, enriched by either negative or positive selection, expressed the activation markers CD25 (IL-2 receptor alpha), CD71 (transferrin receptor), CD134 (OX40 antigen) and MHC class II. Cells expressing these markers were more numerous in TD lymph from arthritic rats than in lymph from normal rats and they included the majority of large CD4(+) T cells. Thus, arthritogenic effector T cells bearing activation markers are released into the central efferent lymph in the late prodrome of AA. Recruitment of these arthritogenic cells to synovium probably determines the polyarticular pattern of AA.

Cytokine profile of protective anti‐Trichinella spiralis CD4+ OX22− and non‐protective CD4+ OX22+ thoracic duct cells in rats: secretion of IL‐4 alone does not determine protective capacity

We analysed the cytokine profile of a T cell subset (CD4+ CD45 RC-) that confers protection against Trichinella spiralis infection in rats. These CD4+ cells are generated in the gut and appear in the thoracic duct lymph within 72 h after infection. Cytokine mRNA levels for IL-2, IL-3, IL-4, IL-5, IL-10 and IFN-gamma and functional cytokine secretion for IL-4, IL-5, IFN-gamma, TNF-alpha and mast cell differentiation activity were tested in vitro following stimulation with T. spiralis antigens. Compared to a non-protective T cell population (CD4+ CD45 RC+ or CD8+), also isolated from the same thoracic lymph, no significant differences were observed in the levels of mRNA for IL-2, IL-3, IL-4, IL-5, IL-10 or IFN-gamma in the protective CD4+ CD45 RC- cells. However, analysis of the cytokine activities in culture supernatant of these T cell subsets following 24 h stimulation in vitro with T. spiralis antigens showed that significant IL-4 and IL-5 activity but little IFN-gamma or TNF-alpha was secreted by the protective CD4+ CD45- RC- cells. Whereas the non-protective CD4+ CD45 RC+ cells secreted significant levels of IL-4, IFN-gamma, mast cell differentiating activity and TNF-alpha but little IL-5 activity. Non-protective CD8+ cells were found to secrete IL-4 but not IL-5. Production of IL-4 was essentially equal for both protective and non-protective T cell subsets. These findings suggest that the presence or absence of IFN-gamma secretion, rather than IL-4 alone, determines whether a T cell subset has protective activity against T. spiralis infection in rats.

Late Failure of Autologous Marrow Grafts in Lethally Irradiated Dogs Given Anti-Class II Monoclonal Antibody

We established a model of canine marrow autografts after 9.2 Gy total body irradiation (TBI) to study the role of class II antigens in hematopoietic stem cell growth and differentiation. Twenty dogs were given 9.2 Gy TBI, marrow, and intravenous (IV) murine anti-class II monoclonal antibody (MoAb). Infusion of 0.6 mg/kg/d of MoAb H81.98.21, an IgG2a reactive with HLA-DR, on days 0 to 4 after TBI did not prevent initial engraftment, but dogs died with late graft failure. MoAb B1F6, an IgG2a reactive with HLA-DR + DP, had no adverse effect on engraftment, although both MoAbs detect antigens on stem cells. The critical time for the effect of MoAbs is the first 4 days after transplantation. Our findings argue against several pathogenetic mechanisms, including removal of MoAb-coated stem cells by the reticuloendothelial system (RES), canine complement-mediated cytotoxic effects on stem cells, antibody-dependent cellular cytotoxicity, and inactivation of MoAb-coated cells by dog anti-mouse antibody. To distinguish between MoAb-induced damage to microenvironment (ME)/accessory cells (AC) and late graft failure from a lack of pluripotent stem cells, three dogs were given TBI, a marrow autograft, and MoAb H81.98.21 on days 0 to 4; one, given thoracic duct cells on day 6, developed graft failure; the other two, given marrow depleted of AC by L-leucyl L-leucine o-methyl ester (Leu-Leu-OMe), had sustained grafts. Findings support the notion that originally transplanted pluripotent stem cells are no longer present on day 6 and that the ME is functional and able to support newly injected stem cells.

Late failure of autologous marrow grafts in lethally irradiated dogs given anti-class II monoclonal antibody

We established a model of canine marrow autografts after 9.2 Gy total body irradiation (TBI) to study the role of class II antigens in hematopoietic stem cell growth and differentiation. Twenty dogs were given 9.2 Gy TBI, marrow, and intravenous (IV) murine anti-class II monoclonal antibody (MoAb). Infusion of 0.6 mg/kg/d of MoAb H81.98.21, an IgG2a reactive with HLA-DR, on days 0 to 4 after TBI did not prevent initial engraftment, but dogs died with late graft failure. MoAb B1F6, an IgG2a reactive with HLA-DR + DP, had no adverse effect on engraftment, although both MoAbs detect antigens on stem cells. The critical time for the effect of MoAbs is the first 4 days after transplantation. Our findings argue against several pathogenetic mechanisms, including removal of MoAb-coated stem cells by the reticuloendothelial system (RES), canine complement-mediated cytotoxic effects on stem cells, antibody-dependent cellular cytotoxicity, and inactivation of MoAb-coated cells by dog anti-mouse antibody. To distinguish between MoAb-induced damage to microenvironment (ME)/accessory cells (AC) and late graft failure from a lack of pluripotent stem cells, three dogs were given TBI, a marrow autograft, and MoAb H81.98.21 on days 0 to 4; one, given thoracic duct cells on day 6, developed graft failure; the other two, given marrow depleted of AC by L-leucyl L-leucine o-methyl ester (Leu-Leu-OMe), had sustained grafts. Findings support the notion that originally transplanted pluripotent stem cells are no longer present on day 6 and that the ME is functional and able to support newly injected stem cells.

Characterization of the thoracic duct T‐helper cells that co‐mediate, with antibody, the rapid expulsion of Trichinella spiralis in adult rats

Thoracic duct cells that act synergistically with immune serum or antibody to transfer rapid expulsion of a challenge infection with Trichinella spiralis muscle larvae were characterized as OX38+, OX8-, OX22- T helper cells. Protective capacity was confined to the dividing T helpers that appeared on days 3-5 in the thoracic duct of rats during a T. spiralis infection. To realize their intestinal priming potential in recipient rats. MHC-compatibility between donor and recipient rat was required. Fractionation of immune serum with 40% saturated ammonium sulphate left transferable protective activity in both the precipitate and supernatant fractions. Absorption of immune serum with muscle larvae antigen removed the capacity to transfer protection.

Synergistic interaction between immune serum and thoracic duct cells in the adoptive transfer of rapid expulsion of Trichinella spiralis in adult rats

Rapid expulsion of Trichinella spiralis could be transferred to naive adult rats with thoracic duct lymphocytes and immune serum. Thoracic duct cells collected from Days 3–5 and immune serum collected on Day 28, respectively, after infection were effective. Both cells and serum were unable to transfer rapid expulsion when given alone, even in large volumes. Recipients of immune serum and cells eliminated a significantly higher number of larvae than control rats by 1 hr after challenge with muscle larvae. Rapid expulsion produced 30–80% larval worm rejection but could not be increased by the transfer of more cells or immune serum. Mucus trapping did not appear to play a role in the rejection process. After transfer of 2 × 10 8 cells and 4.0 ml immune serum, rapid expulsion persisted for less than 1 week. However, after adoptive transfer of cells alone, the gut remained functionally receptive to the passive transfer of immune serum for 7 weeks. Therefore, the changes effected by transfer of cells were long lived in contrast to the 1 week, or less, of functional persistence by transferred immune serum. The data indicate that two separate processes, one cell mediated and the other immune serum mediated, interact synergistically in the intestine and lead to the expression of rapid expulsion.

Effects of thymectomy, thoracic duct drainage, and radiation of T and B lymphocyte distribution and cardiac allograft survival in rats.

The effects of several widely used lymphoid ablative procedures designed to deplete rats of T lymphocytes have been examined. These studies emphasize both the distribution of T and B lymphocytes in individual host lymphoid compartments and the survival of cardiac allografts in recipients modified by various means. Adult thymectomy reduced the numbers of T lymphocytes in the thoracic duct (TD) and lymph nodes and to a lesser extent in the spleen, but did not alter circulating T cell numbers or cardiac graft survival. TD drainage performed alone or in combination with adult thymectomy reduced circulating T cells but did not prolong graft survival. In contrast, indefinite cardiac survival occurred in “B” rats, animals undergoing adult thymectomy, total body irradiation, and reconstitution with syngeneic bone marrow cells from TD-drained donors. However, B rats were not only profoundly depleted of T cells but also of B cells. Infinite graft survival in these recipients appears to represent a true immunological deficit since passive transfer of cells and sera from B rats with long-term surviving grafts failed to influence survival of test heart grafts in unmodified syngeneic recipients. Additionally, thymocytes, lymphoid cells, and TD cells from unsensitized rats or splenocytes from sensitized rats restored the capacity of the B recipient to reject then-grafts acutely. Thus, operative manipulations required to obtain profound depletion of T cells not only may result in prolonged cardiac graft survival but may also cause significant depletion of certain B cells. The less extensive ablative procedures of adult thymectomy or TD drainage only decrease T cells in selected compartments in rats; however, distribution of the effected T cells differ from those previously reported in mice undergoing similar procedures.

Cells of the marginal zone of the spleen are lymphocytes derived from recirculating precursors.

The origin of the B cells of splenic marginal zones was studied using transfer experiments in rats depleted of marginal-zone cells. Cyclophosphamide given as a single dose of 500 mg/m2 was used to deplete the marginal zones. Approximately 90% depletion was still apparent 10 days after treatment. Fetal liver cells did not induce rapid repopulation of the marginal zone. Also bone marrow cells from rats depleted of recirculating lymphocytes were inefficient in this respect. Conversely, thoracic duct lymphocytes and bone marrow cells from normal rats were efficient at restoring marginal-zone cell numbers in cyclophosphamide-treated rats. Thoracic duct cells passaged through an irradiated intermediate host and collected from that host's thoracic duct were also efficient at achieving marginal-zone reconstitution. In rats receiving 1000 rd whole body irradiation, which were protected with fetal liver cell transfer, marginal zones did repopulate at about 3 weeks. It is concluded that marginal-zone B cells, after leaving primary lymphoid organs, enter the recirculating pool for a period of at least several days before settling in the marginal zone. The turnover rate of marginal-zone cells was assessed using tritiated thymidine infusion. Most marginal-zone cells were not labeled after 5 days continuous labeling suggesting that the marginal-zone B cells are not rapidly dividing.

The architecture of rat lymph nodes. III. The lymph nodes and lymph-borne cells of the congenitally athymic nude rat (rnu).

The lymph nodes (LN) of the congenitally athymic nude rat(rnu) were compared with the LN of non-nude littermates. The mesenteric and coeliac LN were smaller in the rnu rats, but the axillary and the cervical LN were larger. Germinal centres were found in the LN of nude rats. They were scarce and often very small, but some were of normal structure, especially in the cervical LN. The endothelium of post-capillary venules in the LN or normal rats, was seen. The paracortex was extremely depleted of lymphocytes but remained a distinct area occupied predominantly by pale interdigitating cells. In some LN the medullary sinuses were distended and the cords engorged with plasma cells. The predominant cells in thoracic duct lymph were immunoglobulin-positive B lymphocytes. The hourly output of these cells was the same as that in non-nude littermates. However, small numbers of thoracic duct cells were positive for the markers identified by the monoclonal antibodies W3/13 and W3/25, although in normal rats these are not expressed on small B lymphocytes.

Nonrecirculating memory T lymphocytes in cellular resistance to infection

Acquired resistance of rats to intracellular infection with Listeria monocytogenes rests on the cooperation between sensitized mediator lymphocytes and effector macrophages. Large numbers of specific T lymphoblasts, capable of transferring resistance to recipients, appear in central lymph shortly (3–6 days) after subcutaneous infection of rats. In contrast, late-phase immunity is poorly transferrable with thoracic duct lymphocytes (TDL) despite high levels of specific resistance observed in spleen, liver, and testes of actively immunized animals. That late-phase immunity is mediated partly by resident, nonrecirculating T cells is attested to by the ineffective transfer of resistance from preinfected to normal partners of parabiotic rats. Transfer studies with thoracic duct cells and peritoneal cells from the stimulated and unstimulated peritoneal cavity seem to suggest that resident T cells mediating late-phase resistance are the progeny of lymphoblasts that extravasated during early phase. Assays measuring the proliferative response upon antigen stimulation in vitro support the concept of a gradual redistribution within the animal of memory T cells.

Immunosuppressive activity of BCG: effects of adjuvant disease, lymphocyte subpopulations, and homing of thoracic duct cells in rats

Administration of BCG by various dosage schedules suppressed adjuvant disease in rats. BCG administration produced an initial increase, followed by a depression, of the phytohemagglutinin response of purified blood lymphocytes. An increase in absolute and relative numbers of bursa-equivalent (B)-cells followed BCG administration, concurrent with a decrease in the phytohemagglutinin responsiveness. With adjuvant alone, there was a diminution in phytohemagglutinin response and an increase in number of B-cells; the latter occurred immediately after adjuvant injection and also when the generalized disease appeared. When both BCG and adjvant were present, parallel increases of phytohemagglutinin responsiveness and B-cell numbers resulted. The pattern of tissue localization of radioactively labeled thoracic duct cells from normal or BCG-treated donors given to normal, BCG-treated, adjuvant-injected, and BCG-treated + adjuvant-injected syngeneic recipients indicated significantly greater homing to the thymus and decreased localization to the bone marrow when BCG had been given to either donors or recipients. When labeled thymus cells were used, only the decreased bone marrow localization was noted. These observations suggest that the suppressive effect of BCG may be mediated through modification of the lymphocyte recirculation pattern, possibly resulting from alterations in lymphocyte recognition sites.

T-cell populations specifically depleted of alloreactive potential cannot be induced to lyse H-2-different virus-infected target cells.

Mouse lymphocyte populations of one parental H-2 type (A) were specificially depleted of alloreactive potential by filtration through irradiated A X B F1 recipients, and thoracic duct cells were then stimulated with virus in an A X B F1 environment. Experiments using T cells that had previously been exposed to influenza virus in the context of A established that cross-priming for recognition of viral components expressed on H-2-different (B) target cells does not occur. Furthermore, immunologically naive T cells stimulated with vaccinia virus, subsequent to negative selection for reactivity to B, could not be shown to interact with virus-infected cells of type B. Either there is no significant T-cell repertoire for recognition of virus associated with an H-2 determinant not encountered during ontogeny, or such T cells are also alloreactive and are removed during filtration.

IgE-B Cell-Generating Factor from Lymph Node Cells of Rats Infected with Nippostrongylus Brasiliensis

Abstract Culture supernatants of mesenteric lymph node cells obtained from Nippostrongylus brasiliensis (Nb)-infected rats have the ability to increase the proportion of IgE-bearing cells in normal bone marrow cell cultures. In order to determine the cell source of the active substance, mesenteric lymph node cells and thoracic duct cells from Nb-infected rats were fractionated by various methods, and culture supernatants of each fraction were examined for the ability to generate IgE-bearing cells in normal bone marrow cell cultures. It was found that culture supernatants of the B cell-enriched fraction were substantially more active than those of the unfractionated cells or T cell-enriched fraction. Residual activity in the culture supernatant of the T cell-enriched fraction was eliminated by prior removal of contaminating immunoglobulin (Ig)-bearing cells in the fraction. The mesenteric lymph node cells depleted of IgE-bearing cells by rosette technique failed to produce IgE-B cell-generating factor. The results indicated that a major source of the soluble factor is IgE-bearing B cells. This conclusion was supported by the fact that treatment of mesenteric lymph node cells with antibodies specific for IgE accelerated the formation of IgE-B cell-generating factor in culture fluids. Formation of IgE-B cell-generating factor in culture fluids. Formation of IgE-B cell-generating factor by the mesenteric lymph node cells was reduced by pretreatment of the cells with pactamycin but not with mitomycin C, indicating that DNA synthesis is not required for the formation of the factor. The appearance of IgE-B cell-generating activity in the culture fluids of mesenteric lymph node cell cultures was inhibited in the presence of dibutyryl cyclic AMP or aminophilline but not by cyclic GMP.

Natural cell-mediated cytotoxicity in rats. I. Tissue and strain distribution, and demonstration of a membrance receptor for the Fc portion of IgG.

Studies in mice and in humans have provided most of the available information concerning natural cell-mediated cytotoxicity. Rats represent a second experimental species which is well suited for the study of natural cytotoxicity. Our studies indicate that the distribution of natural killer (NK)3 cells in rat lymphoid tissues is similar to their tissue distribution in man, with high levels in the blood and spleen and low or undetectable levels in lymph node, thymus, thoracic duct or peritoneal exudate cells. The levels of NK activity varied considerably among various inbred strains of rats. However, the genetic control of levels of NK activity did not appear to be linked to the rat major histocompatibility complex. As recently demonstrated in mice by depletion experiments on antibody-erythrocyte monolayers, many or most rat natural killer cells were found to have surface receptors for the Fc portion of IgG.

Successful cardiac allografts in syngeneic radiation chimeras

Successful cardiac allografts were accomplished across the major histocompatibility complex of rats. LEW and F344 (Ag-B2) rats were lethally irradiated and grafted with WF (Ag-B1) hearts on day 0. Either on day 0 or day 2, the hosts were repopulated with syngeneic hemopoietic cells. The best results were obtained (86%) when a mixture of 3.0 x10(7) non-adherent syngeneic bone marrow and thymus cells were used to repopulate the recipients. In contrast, all of the WF to LEW heart grafts were rejected within 30 days if syngeneic thoracic duct and bone marrow cells were used to repopulate the host. Tolerant rats bearing a functioning WF heart graft were able to mount a normal antibody response to SRBC and a proliferative response to Con A. They accepted a second WF heart or a WF kidney graft but rejected WF skin and bone marrow grafts as well as "third-party" ACl or BN hearts. The lymphocytes of tolerant rats had a reduced response to WF antigens as assayed by local or systemic graft-versus-host reactions in (LEW x WF)F1 recipients. Tolerance to the WF hearts was resistant to a large innoculum of normal spleen and lymph node cells. The unresponsive state could be transferred to unirradiated LEW rats with a mixture of spleen, thymus, lymph node and bone marrow cells.

Frequencies of mitogen-reactive B cells in the mouse. I. Distribution in different lymphoid organs from different inbred strains of mice at different ages

Frequencies of mitogen-reactive B cells have been determined in vitro under culture conditions which allow every growth-inducible B cell to grow and mature into a clone of Ig-secreting PFC. The frequencies of LPS-reactive B cells in the spleen of 6- to 8-wk old mice were between 1 in 3 and 1 in 10 splenic B cells from the following inbred strains of mice: C3H/Tif; BALB/c; BALB/c nu/nu; C57BL/6J; DBA/2J; C57BL/6J x DBA/(2J)F(1); and CBA and A/J. Very similar frequencies are found for lipoprotein-reactive B cells in BALB/c, BALB/c nu/nu, C3H/Tif, and C3H/HeJ mice. No LPS-reactive cells but normal frequencies of lipoprotein-reactive cells were found in C3H/HeJ mice, genetically nonreactive to LPS. SJL mice had significantly lower frequencies of LPS- and of lipoprotein-reactive B cells (1 in approximately 30 B cells). The number of LPS- and of lipoprotein-reactive B cells in spleen was dependent upon the age of the mouse. Newborn spleen contained approximately 10 percent of the number of reactive cells found at 6- to 8-wk of age. From there the frequencies declined again to drop below 5 percent of the maximal number at ages beyond 11 mo. LPS-reactive B cells yielding IgM- and IgG-PFC responses could be found in mesenteric lymph nodes, bone marrow, thymus, thoracic duct, and peripheral blood of 6- to 8-wk old mice. Their frequencies were one in three to five lymph node cells, 1 in 50 to 100 bone marrow cells, one in 10(5) thymus cells, and 1 in 20 to 40 thoracic duct or peripheral blood cells.