Typing for MLC (LD). I. Lymphocytes from cousin-marriage offspring as typing cells.

Abstract

HEN it was observed that the major- ity of SD-identical unrelated individuals stimulated each other in the MLC test, it was postulated in agreement with earlier suggestions by others that MLC activation might be coded by a locus separate from the LA and Four loci.1 " 4 The existence of such a MLC locus is now generally accepted.^About10% of the MLC tests between SD-identical unrelated persons are negative, indicating that a linkage disequilibrium exists between the MLC locus and the LA and Four loci.It is furthermore likely that SD-identical unrelated individuals who are also LD-identical carry MLC determinants that occur rather frequently.In this study we tried to recognize the MLC-locus determinants.To this end we used lymphocytes from double-homozy gous offspring of cousin marriages.As shown in Table 1, it is possible with these cells to indicate whether another cell carries the same MLC determinant and if so whether the determinant occurs in a homozygous or heterozygous form.We will refer io the lymphocytes obtained from the double-homozygous cousin-marriage offspring as typing cells.Typing cells are for LD the equivalent of typing sera for SD.