82 Abstracts

#75 7.6

DIFFERENTIAL FUNCTION OF THE CD8 ~/ot HOMODIMERS AND CD8 /~ HETERODIMERS ON HUMAN CDS+ CYTOLYTIC T-CELL CLONES.

Linda A. Terry, James P. DiSanto and Neal Flomenberg. Memorial Sloan- Kettering Cancer Center, New York, N.Y. USA.

The CD8 complex consist of two chains, a and /3 which can pair to form a/c~ homodimers or ~//3 heterodimers. Previously, we have shown that CD8+ NK cells and TCR ~, 8 cells only express CD8 c,/~ homodimers, while TCR ~//3 cells can express both forms. To date, the known properties of CD8 have been attributed to the CD8 a chain alone, and the functional importance of the CD8 ~ chain remains unknown. We have studied the relative expression of CD8 cz/c, homodimers and CD8 a/19 heterodimers on human cytolytic T- cell clones during activation. Flow cytometry of these clones showed that the fluorescence intensity of cells stained with a mab recognizing the CD8 a//~ heterodimer is consistently lower than the fluorescence intensity seen with a panel of mabs recognizing the CD8 a chain indicating that homodimers represent the predominant form on the cell surface. In addition, CD8 a//~ heterodimers appear to be preferentially down regulated after treatment with phorbol ester (similar to the down regulation of CD4 and CD3). Cytotoxicity studies indicate that mabs reacting with the CD8 ~//~ heterodimer are more efficient at blocking lytic activity than CD8 ~ mabs, despite the fact that heterodimers represent only a subset of the total CD8 complexes. Together these data suggest differential functions for CD8 c,/c, homodimers and CD8

/# heterodimers on cytolytic T-cell clones, and indicate an important role for CD8 ~ in T-cell mediated cytotoxicity.

#76 8.1

OLIGONUCLEOTIDE MATCtIING FOR DRw52 SUBTYPES AND DRw53 It~ I(IDNEY TRANSPLA)ITATIOtl. B tterbut, D McCloskey, J Ilolmes, JA Sachs & PA Biro, tlistocompatibi,qty Research Group, London ttospital ?,Iedical College, Turner Street , London E1 2AD, England

The importance of matching for DRB1 gene products (HLA-DR) in kidney graft survival is well established. The products of the DRB3/4 genes, DRw52 and DRw53, are in strong linkage disequilibrium with DRB1 alleles but are much less polymorphic. Therefore, in order to improve matching prospects and graf t survival, we are assessing the ef fec ts of matching for the DRw52a, b and e subtypes and DRw53 by oligonucleotide typing re la t ive to matc;~in~ for DR.

Crude DI'~A lysates were prepared from eryopreserved donor and recipien. lymphocytes by heat treatment and proteinase K digestion. The DRBI. DRB3 and DRB4 genes were amplified by the polymerase chain reaction (PCR) using DRB-specific primers. The PCR products were fixed onto nylon membranes by Southern transfer or by dot-blotting. Membranes were hybridised with DRw52a, b and c and DRw53 specific oligonucleotide probes at high stringency, to allow discrimination of single base matches.

In the first instance, 69 DR compatible donor-recipient pair~ were examined. Of 16 recipients who were DRw52a, b and c incomoatible, 3/16 (19%) had failed grafts compared to 4/46 (13%)of those who were Dr w52a, b and c compatible. These numbers are limiting and do not reach sI~.atistical significance. Testing is now complete on a second group of 10C serologically DRw52/53 cornpatible but DR incompatible richer-recipient hairs. From the preliminary analysis, it appears that the DRw52a, b and c and DRw53 matched pairs in this group have the same survival rate as the DR matched pairs, although detailed analysis is not yet complete. This may indicate that matching for DRw52a, b and c and DRw53 may be as significant as matching for DR in predictin~ ~raft survival.