Allogeneic lymphocyte stimulation by human spleen: Identification of cells that are very effective for presenting class II HLA antigens

Human spleen cells were fractionated by percoli den-sity gradient centrifugation and by sorting in the FACS with mixtures of fluorescent antibodies against T cells, B cells, monocytes, and Sig-bearing cells. Cells responsible for powerful MLR stimulation were class II HLA antigen-positive and were concentrated in preparations depleted of all the markers listed above. These cells represented 1—2% of the initial spleen cells. They were remarkably more active than other HLA class II anti-gen-positive cells. The procedure described allows rapid enrichment for the responsible cells. It should be useful for further characterization of these cells and for performing studies on their function.