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Horse anti-rabbit bone marrow cell antiserum was tested for its cytotoxic activity with respect to the lymphocytes of the various lymphoid organs. The unabsorbed antiserum was highly cytotoxic with respect to the circulating WBC and cells of the bone marrow and thymus but demonstrated low cytotoxic activity with respect to spleen, lymph node and SAPP cells (sacculus rotundus, appendix and Peyer's patches). However, following absorption with thymocytes, lymph node cells or SAPP cells, cytotoxic activity directed toward any of these cell types disappeared without affecting the cytotoxic activity with respect to bone marrow and circulating lymphocytes. On the other hand, bone marrow and spleen cells and circulating white blood cells were capable of absorbing out completely the cytotoxic activity directed toward these cells, On the basis of a comparison of efficiency of absorption of anti-bone marrow cell activity by cells of the different lymphoid organs and cytotoxicity assays of the absorbed antiserum, it is concluded that approximately 15-25 per cent of the spleen lymphocytes and 20-40 per cent of the circulating lymphocytes in the rabbit are bone marrow-derived cells. The other lymphoid organs do not normally appear to possess these cells. [ABSTRACT FROM AUTHOR]

A comparative study of B cells present in human bone marrow and blood was performed. In both compartments the cells carrying the Ig receptors were found to be small mononuclear cells. Predominance of IgM receptors was found on bone marrow cells whereas Ig receptors present on peripheral blood cells were predominantly of the IgG class. Bone marrow lymphoid cells of non-sensitized donors were capable of binding a primary antigen, keyhole limpet haemocyanin (KLH) and could be retained on glass bead columns coated with either KLH or with goat anti-human IgM antiserum but not with anti-IgG. Whereas bone marrow cells of donors immunized with KLH 16-27 days earlier lacked KLH reactive cells, the latter cells could be demonstrated in the blood. It is concluded that human bone marrow B cells carrying IgM receptors are essential for the early antigen recognition step following which recruitment of these cells into the circulation takes place. [ABSTRACT FROM AUTHOR]

The distribution of bone marrow-derived cells, thymus-derived cells and tissue-bound immunoglobulin was examined using indirect imrnunofluorescence. It was demonstrated that primary follicle small lymphocytes are bonemarrow derived in the absence of the thymus, they lack thymus-associated antigens, and bear high concentrations of surface-associated immunoglobulins. Thymusantigen positive cells make up the majority of, if not all, diffuse cortex lymphocytes, do not bear concentrations of surface immunoglobulin detectable in this system, are found as rare cells in primary follicles, and are present in germinal centres. A mechanism is proposed for the thymus-bone marrow interaction in the immune response. [ABSTRACT FROM AUTHOR]

The impaired antibody response of' neonatally bursectomized chickens was restored by bone marrow cells from normal—but not from bursectomized— syngeneic donors. Chimaerism of donor cells in the recipients was demonstrated using the sex chromosomal marker. Attempts to substitute autologous bursal cell suspensions for the bursa in situ were unsuccessful. It is concluded that B lymphocytes in chicken bone marrow have matured in the bursa. [ABSTRACT FROM AUTHOR]

Lethally-irradiated mice were injected with rat bone marrow cells and examined subsequently for the presence of rat macrophages, using an indirect fluorescent antibody test in conjunction with a fluorochrome-labelled phagocytic cell marker. Donor bone marrow cells were fractionated by (1) adherence, (2) magnetic removal of phagocytic cells containing ingested carbonyl iron and (3) treatment with lymphocyte-absorbed anti-rat macrophage serum either in vitro or in vivo. Extensive rat cell proliferation occurred in the resulting xenogeneic chimaeras by or after Day 4 and increased during the next week. The precursor of both the free and fixed macrophages was contained in the non-adherent, non-phagocytic population of bone marrow cells. The anti-macrophage serum was not selective and abolished the capability of bone marrow cells to proliferate. [ABSTRACT FROM AUTHOR]

Results of the present experiments suggest that dividing cells in rat bone marrow can generate lymphocytes capable of initiating a systemic graft- versus-host reaction. In these experiments, Lewis bone marrow cells were incubated in vitro with either tritiated thymidine ([³H] thymidine) or 5-bromodeoxyuridine (BUDR)—agents which inhibit cell proliferation. Bone marrow cells prepared in this way and injected into an intermediate (Lewis × DA)F1 host were unable to pro-liferate and mature into circulating immunologically competent lymphocytes. Concentrations of [³H]thymidine and BUDR which inhibited the development of putative lymphocyte precursors in bone marrow had no obvious effect on the immunological performance of thoracic duct lymphocytes. Lewis lymphocytes, cultivated in medium containing these agents, caused a vicious graft-versus-host reaction in X-irradiated (Lewis × BN)F1 hybrid rats. The results strengthen the view that [³H]thymidine and BUDR exert their inhibitory effect on replicating lymphocyte precursors and not on long-lived members of the circulating lympho-cyte pool.

Peritoneal cells from non-immunized mice, when incubated in vitro with sheep red cells and complement in a film of carboxymethyl-cellulose gum, form plaques of haemolysis after a latent phase of 15–20 hours. Plaques are also produced by the free cells of the pleural cavity but not by lymph node, spleen, thymus and bone marrow cells. Plaques are not produced at room temperature, nor when the complement has been inactivated or the peritoneal cells have been heat-killed. The phenomenon is age-dependent: the peritoneal cells reach the highest activity when the donor mice are about 10 weeks old. By testing purified populations of lymphocytes and macrophages the cell type responsible for plaque production has been identified as the lymphocyte. Plaque formation is suppressed in the presence of an anti-mouse immunoglobulin serum without any detectable effect on cell viability or anticomplementary action. This suppressive effect is destroyed by prior precipitation of the antiserum with normal mouse serum. A technique which facilitates the study of peritoneal cells from individual mice has been developed and applied to peritoneal cells from Friend virus-infected mice. The activity of peritoneal cells 10 days after intravenous or intraperitoneal infection is similar to that of their uninfected counterparts. Peritoneal cells from mice killed 17 days after intravenous infection or 19 days after intraperitoneal infection form significantly reduced numbers of plaques. The reduced activity is accompanied by a decrease in the percentage of lymphocytes present in the peritoneal population of the infected mice. [ABSTRACT FROM AUTHOR]