A novel role for macrophage: antigen discrimination of distinct carbohydrate bonds

Alterations in lymphocyte recognition repertoire during ageing. I. Analysis of changes in immune response potential of B lymphocytes from non-immunized aged mice, and the role of accessory cells in the expression of that potential

The repertoire of specificities recognized by endogenous plaque-forming cells of young or aged mice has been examined, as well as the repertoire of specificities represented by mitogen-activated B cells of those animals. Significant changes occur in both polyclonal endogenous plaque-forming cells and polyclonal B cell responsiveness, as well as reactivity for antigens expressed on bromelain-treated mouse erythrocytes and mouse Ig-coupled sheep erythrocytes. Adoptive transfer experiments suggest that these changes reflect a role for the differentiative environment in the regulation of the B cell recognition repertoire. Additional analysis of changes in antigen-presenting cells in aged mice suggest that alterations in the manner of presentation of environmental antigens in vivo may control the expressed B cell repertoire. Indeed, under experimental conditions it has proven less easy to induce B cell/macrophage restriction (for antigen presentation and induction of antibody formation) in cells of old animals than in cells of younger mice.

Elimination of allogeneic lymphocytes by mice

Two major classes of response to allogeneic lymphocytes can be detected in mice in vivo, based on injecting them intravenously with 51Cr-labelled lymph node cells and examining them in a short term assay. A natural immunity discriminating between allogeneic and syngeneic lymphocytes is seen in the lymph nodes (and to a lesser extent, the spleen), which has such close similarities to natural cell-mediated responses of the NK class as thymic-independence and radioresistance. However, it has immunological specificity of a conventional kind, probably towards serologically determined K/D antigens. There is also an active immune response, produced by immunisation with dissociated lymphoid cells or allografting, which consists of three elements: an IgG opsonising alloantibody response, diverting circulating lymphocytes to the liver; an IgM opsonin, localising them to the spleen; and a cell-mediated serum-dependent elimination mechanism that destroys cells entering the lymph nodes and spleen. Dose-response curves for the primary response show evidence of high-dose paralysis of elimination. Dose-time-response results for the secondary show a variety of unique characteristics; evidence is presented to suggest that several aspects of the phenomenon betray primitive features retained from an earlier stage in the evolution of the immunological system.

In vitro generation from murine brow marrow cells of accessory cells with discrete antigen presentation capacity and ability to release lymphostimulatory molecules

An investigation of the immunological accessory cell function of in vitro bone marrow derived colony forming cells has been made. Data are presented to show that such cells can present immunogenic stimuli to lymphocytes and release lymphostimulatory products that in turn replace certain macrophage functions in the immune response. The appearance of these two activities is not correlated. Considerable heterogeneity exists in terms of the ability of different populations of cells to present distinct carbohydrate antigens in immunogenic form. In addition, that different macrophage cell populations can alter the affinity of antibody produced by an optimally stimulated primed spleen cell population is reported.