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Rabbit appendix cells were injected into horses at weekly intervals, after which the horses were bled and the sera tested for cytotoxic activity. The unabsorbed antiserum was cytotoxic to the lymphocytes of all the lymphoid organs tested Following absorption with bone marrow and thymus cells, the antiserum lost all cytotoxic activity directed toward these cells but displayed almost undiminished cytotoxic activity toward the cells of the SAPP organs (sacculus rotundus, appendix and Peyer's patches). The absorbed antiserum also demonstrated cytotoxic activity toward certain lymphocytes present in the spleen, lymph node and circulation. Thus, the antibodies directed toward the antigens common to all lymphoid cells were removed by the thymus and bone marrow cells, leaving behind cytotoxic antibodies directed toss aid antigens present on appendix and appendix-derived cells only, We have therefore succeeded in preparing antisera specific for rabbit thymus, bone marrow and appendix cells, respectively. [ABSTRACT FROM AUTHOR]

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]

The contribution of syngeneic bone marrow and thymus cell populations obtained from normal and cortisone-treated donor mice for reconstitution of delayed hypersensitivity to methylatcd human serum albumin (MHSA) was studied in lethally irradiated recipients employing a limiting dilution assay. Normal thymus cells contained at least one antigen-reactive cell (or cell unit) per 3.7 × 107 cells, while cortisone-resistant cell populations contained one cell per 6.7 × 105 cells. Thus, cells immunocompetent to MHSA are not destroyed by steroid. Bone marrow cell populations contribute effector cells, and as few as 2 × 106 cells are capable of fully restoring delayed response when combined with optimum numbers of thymus cells. Large numbers of thymus cells alone will restore immune responsiveness, indicating that such populations do contain some effector cells, either as contaminating blood borne cells, or as glandular cells derived possibly from sinusoids. Similarly, bone marrow cells in larger numbers restore responsiveness, implying contamination with thymus-derived cells. [ABSTRACT FROM AUTHOR]

Bone marrow cells and thymus cells were observed in cell transfer expehments to collaborate in the production of anti-BSA antibodies. The target cells for tolerance induction either with a 'low dose' of antigen (100 µg of deaggregated BSA once a week × 5) or with a 'high dose' (a single injection of 5000 µg) were identified by the same technique. In 'low dose' tolerance, some indication was obtained that thymus-derived cells in peripheral lymphoid systems were the target cells; bone marrow-derived cells appeared not to be so susceptible, and the cells residing in thymus or bone marrow seemed to remain unimpaired, in contrast, the injection of a 'high dose' of tolerogen rendered both types of cells in spleen, thymus cells and bone marrow cells, unresponsive or hyporesponsive in parallel with one another. [ABSTRACT FROM AUTHOR]

The purpose of this investigation was to compare and contrast the migratory behaviour of three sub-classes of spleen lymphocytes in the mouse: cells capable of adsorbing a specific labelled antigen on to their surfaces ('antigenbinding' cells); bone-marrow-derived ('B') cells; and thymus-derived ('T') cells. Antigen-binding spleen cells were labelled in vitro with 125l-polymerized flagellin from Salmonella adelaide and injected intravenously into syngeneic recipients. Their distribution within the spleen was studied by radioautography for 24 hours after injection. Nearly all the antigen-binding cells localized and accumulated in and around the germinal centres of the white pulp. Bone-marrow-derived B-spleen cells which were labelled in vitro with ³H-uridine were found to localize in and around germinal centres. The proportion of B cells found in these regions was lower than the proportion of antigen-binding cells and there was not a progressive aggrregation of B cells over 48 hours. Thymus-derived T-spleen cells also labelled in vitro with ³H-uridine were located predominantly in the established thymus-dependent periarteriolar regions of the white pulp. The significance of the localization of antigen-binding cells in the germinal centre regions of spleen is discussed in relation to the B and T components of the spleen lymphocyte population. The conclusion was reached that B lymphoytes activated by contact with antigen Iodged preferentially in germinal centre areas. [ABSTRACT FROM AUTHOR]

The injection of polymerized flagellin into C57BL mice increased the number of granulocyte cluster-forming cells and macrophage colony-forming cells in the bone marrow. The addition of polymerized flagellin to agar cultures of bone marrow cells from normal or antigen-injected mice increased the number and growth rate of macrophage colonies developing when mouse serum was used as the source of colony stimulating factor (CISF). Polymerized flagellin had no potentiating effect on colony growth when urine or medium conditioned by bone marrow, spleen, lymph node or thymic cells were used as the source of CSF. Antigens may stimulate the proliferation of granulocyte and macrophage precursor cells by an indirect mechanism involving the production by bone marrow cells of CSF, or a similar growth promoting factor. [ABSTRACT FROM AUTHOR]

The incorporation of some antigens such as bacterial endotoxin, heterologous erythrocytes and bacterial flagellin preparations can enhance the formation of colonies in cultures of normal mouse bone marrow or foetal liver cells in vitro. Other antigens such as foreign serum proteins and haemocyanin are inactive. This effect depends on the reaction of antigen with a component of normal mouse serum. [ABSTRACT FROM AUTHOR]

The enhancement effect of some antigens on in vitro colony formation by normal mouse bone marrow cells is mediated through a normal serum αmacroglobulin (αM) which is present in newborn animals and shows no immunological specificity. The proportion of antigen and αM affects colony enhancement, and it has also been shown that specific antibody successfully competes with αM for the antigen. It seems likely that antigen-αM complex acts directly on the colony forming cell, rather than indirectly through release of colony stimulating factor. The possible relevance of this phenomenon to immune induction and, to the effect of antigens in promoting irradiation survival is discussed. [ABSTRACT FROM AUTHOR]

It has been shown that intraperitoneal injection of Freund's complete adjuvant can stimulate the multiplication and effect the distribution within the animal of cells which form granulocytic and monocytic colonies in vitro. This response is associated with a leukocytosis and a fall in haematocrit. A variety of antigens were tested all of which resulted in an increase in the number of colony forming cells in the spleen to a greater or lesser degree. Two mechanisms are thought to be involved in this response: (1) with some antigens a direct stimulation of colony forming cells by an antigen-α-macroglobulin complex; and (2) an indirect stimulation of colony forming cells by release of colony stimulating factor from cells other than the colony forming cells. [ABSTRACT FROM AUTHOR]

The persistence of immunogenicity of lipopolysaceharide antigens of E. coli and of sheep red blood cells in the mouse was studied by a transfer system. Immunized mice were lethally irradiated and re-populated with non-immune syngeneic lymphoid and bone marrow cells at different times after immunization. Persistence of immunogenicity in the irradiated hosts was revealed as the induction of a primary immune response in the transferred cells. In this system SRBC persisted in an immunogenic form for 14 days whereas the bacterial antigens remained immunogenic for at least 45 days.