Differences in specificity of “DPw2‐specific” cytotoxic T cell clones revealed with HLA‐mutant lines: Evidence that non‐DP HLA genes influence recognition by some clones

Abstract

Seven allospecific cytotoxic T lymphocyte (CTL) clones derived from DPw2-specific bulk populations were characterized by three approaches to obtain a more detailed understanding of the T cell recognition of the HLA-DPw2 molecule. All seven of the clones were DPw2 specific and indistinguishable in specificity by three approaches: (a) patterns of lysis of panels of targets from normal donors; (b) inhibition of lysis by anti-class II monoclonal antibodies (mAb); (c) lysis of mutant lymphoblastoid B cell lines (LCL) with isolated loss of DP2 alpha or DP2 beta gene expression (as a result of selection for resistance to DPw2-specific CTL). However, only four of the seven CTL clones (which we designate "orthodox") lysed all mutant DPw2+ LCL tested; the other three ("heterodox") CTL clones showed reduced or no lysis of particular LCL which expressed DPw2 but had been mutagenized and selected for loss of DR expression. Cold target blocking experiments with the mutant LCL confirmed differences in: (a) specificity among CTL clones and (b) CTL-defined phenotype among serologically indistinguishable DR-DPw2+ mutant LCL. Differences were not explained by different levels of DP expression by the mutant LCL. Given the nature of the mutagens and mutations, it is highly improbable that point mutations in DP account for differences in recognition. These data suggest that non-DP HLA genes influence recognition by some DP-specific clones, potentially due to corecognition of HLA-DR alpha or another non-DP HLA product in the context of a DPw2 alpha/beta dimer.

T-Cell Epitopes and Human Leukocyte Antigen Restriction Elements of an Immunodominant Antigen ofBlastomyces dermatitidis

“…LCL .45, expressing only one parental HLA allele, does not have a HLA-DP allele that matches those of the T-cell clones. LCL EM5 and LCL EM13, HLA-DP loss mutants derived from .45 (22), lack surface HLA-DP (Fig. 5A).…”

“…Introduction of specific HLA-DR B genes into the founder cell line yielded transferents, each of which expressed just one or another kind of HLA-DR␤ molecule (18). HLA-DP transferents were created here by means of gene transfer with episomal vectors into HLA-DP null mutants that had been derived originally (22) from the parental 721 cell line heterozygous at the DP locus (haplotype DPw4/2). cDNAs encoding either the DP␤w4 chain or DP␣w4 chain were isolated from a cDNA library constructed with mRNA from the parental LCL 721 cell line using standard screens and cloned into pRSV.5 (neo) plus ori P. Two independent HLA-DP loss mutants, devoid of surface HLA-DP due to defects in either the DP␣ or DP␤ chain gene (22), served as the recipients for gene transfer.…”

“…Initially, a DP␣4 gene was transferred into EM13, which specifically lacks a DP␣ chain (22), giving rise to transferent EM13/17-3B, which displays a surface HLA-DP heterodimer of a DPw4␣ chain and the endogenous DPw2␤ chain (Fig. 5A).…”

“…6B). Subsequently, we transferred a DP␤4 gene into cell line EM5 to construct transferent 3C1, which displays surface HLA-DP heterodimers composed of the endogenous DPw2␣ chain (22) and a DPw4␤ chain (Fig. 5A).…”