Activation of Human T and B Cells by Rabbit Anti-Human beta2-Microglobulin

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Abstract
Rabbit anti-human .beta.2-microglobulin (anti-.beta.2m) increased the highest [thymus-derived] DNA synthesis in unseparated lymphocytes or artificially composed mixtures enriched in T [thymus-derived] and B [bone marrow-derived] cells. In enriched T and B cells. In enriched T and B cells no or low stimulation was seen. The maximal response by Ig[immunoglobulin]G anti-.beta.2m was seen in proportions of enriched T/B cells, being 3:1 for blood lymphocytes and 1:1 for spleen cells, which are the same as the physiological proportions of T and B cells in these lymphoid organs. Unseparated lymphocytes gave a peak response on day 3 and enriched B cells had a peak response on day 6. Fab anti-.beta.2 did not activate enriched T cells but increased DNA synthesis in enriched B cells to about the same extent as unseparated lymphocytes and mixtures of enriched T and B cells. The proportion of sheep erythrocyte rosette-forming cells (E-RFC) decreased after stimulation by anti-.beta.2m and increased after stimulation by phytohemagglutinin. As revealed by autoradiography, a proportion of lymphocytes activated by anti-.beta.2m were E-RFC and this proportion increased with increasing stimulation by anti-.beta.2m. DNA synthesis induced by anti-.beta.2m was unchanged for spleen cells and slightly decreased for blood lymphocytes when phagocytic cells were removed by Fe treatment. Supernatants from lymphocytes activated by anti-.beta.2m only induced low DNA synthesis in enriched T or B cells. Experiments with mitomycin-treated cells indicate that cooperation and close contact between T and B cells are needed for activation by IgG anti-.beta.2m. T cells are needed for B cell activation by anti-.beta.2m and B cells are required for T cell activation to occur.