In vitro cytotoxicity by human lymphocytes from individuals immunized against histocompatibility antigens. II. Relation to HL-A incompatibility between effector and target cells.

Lymphocytes from humans immunized by allogeneic skin grafts destroyed fibroblast monolayer cultures derived from the skin donor. Cytotoxicity also developed on several allogeneic fibroblast monolayers from unrelated persons. HL-A typing showed that all of these allogeneic fibroblasts shared one or more HL-A antigens with the skin donor.

In vitro assay of cell-mediated immunity: the inhibition of migration of sensitized human lymphocytes by HL-A antigens.

Human blood lymphocytes from donors sensitized by skin grafting were inhibited in their migration from capillary tubes by antigens from the skin graft donor. Lymphocytes from non-sensitized human subjects showed no or a very slight inhibition with similar antigens. When confronted with cell antigens from individuals which did not possess any of the detectable HL-A specificities of the donor, the sensitized lymphocytes exhibited a marginal degree of inhibition (15·3±2·0%).

Rapid lymphocytic recognition of histoincompatibility. Changes of the deoxyribonucleoprotein complex in mixed cultures of allogeneic human lymphocytes.

The mechanism of growth stimulation in allogeneic lymphocytes mixed in vitro was studied at the cell level by means of cytophotometric techniques. A pronounced increase in fluorescence intensity of fixed and acridine orange (AO) stained lymphocytes was observed as soon as after 1-3 hr in mixed culture. No increase in the amount of DNA took place during this time.