14 Abstracts

B-2.1 #15

POPULATION STUDY OF AN UNUSUAL HLA-B41,DR4(DRBI*0405),DQ2 HAPLOTYPE. C.Wolfe and EJ.BalI. Community Blood Center and Wright State University, School of Medicine, Dayton, OH.

A blood donor with an unusual A2,B41,DR4,DQ2 haplotype was identified. To determine if the DR4,DQ2 association was common to HLA-B41 haplotypes, a population study was under- taken. 95 unrelated B41-positive Caucasians (including the propositus) found among normal donors were compared to 3214 B41-negatives. 69 of the 95 B41-positive and 364 of the B41 negative donors were also typed for Class II. Non-B locus alleles showinq statistical variation are shown below:

B41 Ag B41 Ag B41 Ag B41 Ag Aq + + + - + - X 2 p A23 9 86 120 3094 8.11 .0044 A26 32 63 166 3048 133.41 <.0001 A3 12 83 920 2294 11.67 .0006 DR6 31 38 103 261 7.51 .0061 DR10 4 65 6 358 4.43 .0353 Neither A2 nor DR4 were statistically increased in this analysis. However, of the 26 B41,DR4-positive individuals, 5 were inferred to have a DR4,DQ2 haplotype, which was significant (p<.0001). A2 was present in 4/5 of these (3 being probable A2 homozygotes) . Two of the 5 DR4,DQ2 individuals were typed for DR-beta by PCR-SSP and both were found to be DRBI*0405. These data suggest an A2,B41, DRBI*0405,DQ2 haplotype in linkage disequilibrium in the Caucasian population. The apparent strength of the B41,DR4,DQ2 association is perhaps indicative of recent introduction of the haplotype into the population from another group or as the result of a recombinational event.

B-2.1 #16

DR7 POLYMORPHISM IS NOT ENCODED BY THE SECOND EXON OF DRB1, DRB4, DQA1, DQB1, DPA1 NOR DPBI. LA Guethlein, WB Bias, JM Hart, F Robbins, BJ Schmeckpeper, Center for Medical Genetics, Johns Hopkins University, Baltimore, MD.

in 1983, Hsu et al. described an 11 member family in which three DR7 bearing haplotypes were segregating. The father was A29,B27,DR3,DR52,DQ2,DP4/A3,B47,DR7,DR53,DQ2,DP2.The mother was A2,B57,DRT, DQg, DP4/A1,B13,DR7,DQg, DP4. Although she appeared to be homozygous for DR, DQ and DP, in MLR her cells stimulated those of her husband and all children. Children with the same paternal haplotype but different maternal haplotypes were mutually stimulatory. The goal of these studies was to identify the sequence variation responsible for this polymorphism by sequencing the class II loci.

Various strategies were utilized to obtain DNA sequence, starting with PCR amplified products. These strategies included cloning PCR products prior to sequencing, sequencing by oligonucleotide typing, sequencing PCR products from reverse transcription of mRNA, and direct sequencing of PCR products. The second and third exons of DRB1 and the second exons of DRB4, DQA1, DQB1, DPA1 and DPB1 were sequenced.

Contrary to expectation, both of the mother's alleles at DRB1 were identical in the regions sequenced; as expected, both DRB4 alleles were DRB4-nulI, because of a mutation in a splice codon. Similarly, she was homozygous in exon 2 of DQA1, DQBt, DPA1 and DPB1. The father's DR7 haplotype was identical in DNA sequence to his wife's except for the DQB1 allele; he was DQB1*0201 whereas she was homozygous for DQBt*03032.

There were no DNA sequence differences identified to account for the cellular reactivity within this family. We have, however, one serologic correlate of the MLR. Three alloantisera are used in our laboratory to detect DR53. Prior to absorption, these sera also contain anti-DR7. Absorption with the B57,DR7,DQ9,DR53null HTC removes reactivity to all DR7 + cells in two sera; however, the third serum, JH-Harris, although diminished in reaction strength, remains cytotoxic to cells bearing Bt3,DR7,DQ9,DR53nulI. Absorption with cells of this haplotype completely removes cytotoxicity to all DR7-bearing cells.