Observations upon DNA synthesis and the cytotoxic response of leucocytes after mixed culture and their relation to histocompatibility antigens in man.

Mixed leucocyte cultures performed between identical twins, siblings of one family and unrelated individuals were evaluated by measurement of the uptake of C-thymidine and by their cytotoxic effect upon an allogenic target cell line (Chang liver cells). A close correlation was found between HL-A compatibility and C-thymidine uptake in all three situations, whilst no significant relationship existed between cytotoxicity and either histocompatibility or DNA synthesis. It is suggested that these two reactivities are distinct but are both influenced (although to a different extent) by differences in histocompatibility.