Activation of human lymphocyte subpopulations by rabbit anti-human beta2-microglobulin and by lipopolysaccharide

Rabbit anti-human beta2-microglobulin (anti-beta2m) was found to increase DNA synthesis in peripheral blood lymphocytes (PBLs) and in cells from abdominal lymph nodes, spleen, tonsil, adenoid, appendix, and bone marrow. The response to anti-beta2m was highest in cells originating from abdominal lymph node, appendix, and spleen. These organs were shown to contain a high proportion of surface-Ig-positive cells. No response to anti-beta2m was seen in thymus cells or in B-cell-depleted lymphocyte populations. Lipopolysaccharide (LPS) increased DNA synthesis in spleen cells, bone marrow cells, tonsil cells, and, sometimes, in cells from abdominal lymph nodes but weakly or not at all in PBLs. To study whether anti-beta2m and LPS activated the same subpopulation of lymphocytes, cultures were exposed to both mitogens in various concentrations. The effect on DNA synthesis in spleen cells was almost additive. This may indicate that these two polyclonal B-cell activators (PBAs) stimulate mainly distinct subsets of B cells in spleen. On the other hand, these two mitogens have a synergistic effect on DNA synthesis in PBLs. Since anti-beta2m is the first described selective B-cell mitogen activating human PBLs, it might be of clinical importance in the functional characterization of lymphocyte subpopulations.