Selective depletion and enrichment of alloreactive cytolytic effector lymphocytes using anti-fluorescein affinity columns

Peritoneal exudates from BALB/c mice rejecting C57BL ascites lymphoma EL4 are a rich source of cytolytic effector lymphocytes (CL); however, these preparations are still contaminated even after removal of adherent cells with other mononuclear cells which do not appear to be cytolytic. The relationship of the cytolytic and "non-cytolytic" cells to graft rejection in vivo is not completely understood. We have used anti-fluorescein (α-FL) columns to separate sensitized lymphoid populations into fractions enriched or depleted in cytolytic activity. EL4 were directly labeled with fluorescein isothiocyanate (FL-EL4), centrifuged with CL and the mixture was applied to a column of horse α-FL antibody conjugated to Sepharose 4B. FL-EL4 and lymphocytes bound to them were retained on the column, while non-bound lymphocytes were collected in a medium wash (passed cells). CL bound to FL-EL4 were then eluted with EDTA (eluted cells). Cytolytic activity of the two fractions was compared to that of the unfractionated population in an in vitro ⁵¹Cr release assay. Passed cells were consistently depleted in cytolytic activity compared to unfractionated cells or manipulation controls reaching 100% depletion in some experiments. Enrichment of cytolytic activity in eluted populations was frequently but not invariably observed. Rate of cytolysis was used as a measure of cytolytic activity in fractionated populations. Specificity of binding was investigated in reciprocal experiments using CS7BL/6J effectors raised against BALB/c lymphoma RL♂ 1. Viability of recovered cells was high and the procedure was rapid, efficient and versatile. In contrast to monolayer cellular immunoabsorbents, contamination of fractions with absorbing cells was consistently less than 5%. Both enriched and depleted populations are available for further study of surface markers and function.