Evidence for an unlinked gene which modifies HL-A antigen expression

New groups and segregant series among B-cell alloantigens of the Merrit system. A study of leukemia cells, peripheral B cells, and lymphoblastoid cell lines

On the basis of reactions with a chronic lymphatic leukemia cell panel, evidence for 6 new specificities of the Merrit B-cell alloantigenic system in man is presented, bringing the number of provisionally defined specificities to 19. These can be roughly divided into two segregant series. The system is well represented on both homozygous and heterozygous B-type lymphoblastoid cell lines. In the cell lines some specificities show a suggestive but inexact correlation with HLA-D locus factors. This correlation is represented also on peripheral blood B cells, on the non-T variety of acute lymphatic leukemia cells, and on acute myeloid leukemia cells. Although great similarities exist, each of the cell populations may manifest differences other than or in addition to mere differences in B-cell antigen frequencies.

Expression of HLA-B12 on platelets, on lymphocytes and in serum: a quantitative study

Expression of the antigen HLA-B12 on platelets, on lymphocytes and in serum of normal subjects was studied using several quantitative techniques. HLA-B12 was found to be expressed on platelets from each of 25 heterozygous HLA-B12-positive donors in amounts varying about 35-fold from weakest to strongest. Expression of B12 on platelets was enhanced in the presence of the first locus antigen A11, but decreased in the presence of A2, A3, and Aw28. The antigen was expressed in equal strength on lymphocytes sampled from the same donor population. Serum content of B12 assayed in five subjects was found to be roughly proportional to the expression of that antigen on platelets. Expression of B12 on platelets is under genetic control but the precise mechanism of inheritance has not yet been defined. The applicability of these findings to transfusion of single donor platelets to alloimmunized patients is under investigation.

Histocompatibility testing in dogs. II. Leukocyte typing in relation to the mixed lymphocyte culture (MLC) reactivity

The correlation between MLC reactivity (LD) and serological leukocyte typing (SD) was studied in a beagle colony. Disparity for a serologically defined non-DL-A lymphocyte antigen did not correlate with MLC reactivity. Lymphocytes of colony members with common ancestors and SD identical DL-A haplotypes did not stimulate each other in the MLC. This implies that LD typing in the beagle coolony can be generally predicted by DL-A SD typing. Consequently, lymphocytes of sibs homozygous for a given DL-A SD haplotype could be shown, with few exceptions, to be also homozygous for MLC determinants. Cells of these homozygous sibs can be used in MLC typing as reference cells for DL-A LD specificities. Two exceptions to the expected linkage between DL-A SD typing and MLC reactivity were found. These findings could not be explained by recombination with the DL-A region assuming a single major LD locus coding for MLC. Thus, suggestive evidence for more than one single LD locus has been obtained.

Serotyping for MLC gene products: I. Presumptive evidence that ABCIL may detect MLC factors

Serum from a grand multiparous Inuit (Eskimo) woman, who is HL-A identical but stimulatory in MLC with cells of her husband, contains strong ABCIL reactivity. This serum is operationally monospecific against a cell membrane determinant on lymphocytes, but not platelets, of some unrelated persons. Cells of those who are ABCIL positive with this serum always give a lower MLC stimulation index compared with their MLC responsiveness to cells that are ABCIL negative. This serum also contains good MLC inhibitory activity but only in those one way MLC reactions in which it reacts, by ABCIL, with the stimulating cells. It is postulated that the ABCIL activity is directed against a common MLC factor on lymphocytes.