Isogeneic and allogeneic lymphocyte interactions may be controlled by cell surface immunoglobulin tropism

A study of allogeneic MLC (mixed lymphocyte culture) and two types of isogeneic MLC has been conducted in which subsets of B-cells were serologically removed from pools prior to using the remainder as stimulator cells. Cellular division in the two types of ILC (isogeneic lymphocyte culture) was found to be triggered by lymphocytes with IgG₁ on their surfaces. In contrast, the stimulator cells in ALC (allogeneic lymphocyte culture) possessed membrane-bound IgG_2A and/or possibly IgG_2B. Splenic T-cells were incapable of stimulating replication of splenic or lymph nodal T-cells in the absence of B-cells. Splenic T-cell preparations served as weak stimulators of other allogeneic T-cells but only when B-cells, either isogeneic or allogeneic to the stimulator T-cells, were present. We propose that stimulation in the MLC occurs in two distinct steps. First, immunoglobulins on cell surfaces may function to bring appropriate subsets of cells together. Next, antigenic recognition occurs that results in blastogenesis. Furthermore, the tropism or attraction that certain immunoglobulins have for some cell types may determine which subsets of cells participate in allogeneic and which take part in isogeneic MLC.