Allorecognition of HLA‐DR and ‐DQ transfectants by human CD45RA and CD45R0 CD4 T cells: Repertoire analysis and activation requirements

Abstract

We have investigated the requirements for allogeneic stimulation of human CD4 T cells using HLA class II products expressed on various cellular backgrounds. Human (class II-negative RJ2.2.5 mutant) B cell lines transfected with HLA-DR or -DQ cDNA clones were efficient stimulators for highly purified CD4 T cells. HLA-DR-transfected mouse L cells or IFN-gamma-induced human fibroblasts, although able to function as accessory cells for T cell responses to the mitogen PHA, failed to stimulate strong T cell alloresponses. On the basis of these observations, we have employed class II transfectants to address the following questions: (a) do CD45RA and CD45R0 subpopulations differ in their allogeneic activation requirements, (b) are these subpopulations skewed in their recognition of HLA-DQ vs. HLA-DR in a manner which might support the concept that CD45RA T cells are involved in HLA-DQ-restricted suppressor inducer functions and (c) by using transfectants expressing individual HLA-DR or -DQ heterodimers in combination with limiting dilution analysis, can one for the first time obtain estimates of precursor frequencies for allogeneic cells recognizing each of these class II isotypes? Our results show that CD45RA and CD45R0 T cells respond comparably to optimal numbers of stimulator cells. However, when CD45RA and CD45R0 T cell populations depleted of endogenous accessory cells were cultured with limiting numbers of stimulator cells, CD45R0 cells generally responded more strongly, consistent with the elevated levels of various adhesion molecules known to be expressed by this population. Further, we found a similar representation of responses to HLA-DR and -DQ antigens among populations expressing CD45RA and CD45R0 isoforms. Finally, the precursor frequencies of allogeneic CD4 T cells responding to particular HLA-DR alleles were higher than to -DQ, but only by a factor of about 1.6, indicating that HLA-DQ recognition may occur more frequently than implied from previous antibody blocking studies.

Detection of primary direct and indirect human anti‐porcine T cell responses using a porcine dendritic cell population

“…In alloresponses, HLA-DR also plays a dominant role, although the precursor frequencies of anti-DQ alloreactive T cells was shown in one study to be only twofold lower than the frequency reactive with DR alloantigens [44]. Although other groups have documented proliferative and cytotoxic responses from purified CD8' T cell responders [37], the implication of our experiments using an anti-SLA class I mAb is that in a mixed population of CD4' and CD8' T cells, the proliferative responses of CD4' Tcells predominate.…”

Alloantigen priming induces a state of unresponsiveness in human umbilical cord blood T cells.

“…Medical Sciences: Risdon et al lymphoblastoid B cells, Raji, at a responder/stimulator ratio of 10:1 for 5 days [Raji cells express known co-stimulatory molecules including B7 (15), B70 (15,16), lymphocyte function-associated antigen 3 (LFA-3) (17), and intercellular celladhesion molecule 1 (ICAM-1) (17) and HLA class I and class II major histocompatibility complex (MHC) molecules (17)]; (ii) reisolation of T cells by negative selection; (iii) reculture of cells in medium for 48 hr; and (iv) restimulation with donor or third-party lymphoblastoid B cells at a responder/stimulator ratio of 10:1. Fig.…”

High precursor frequency of human T cells reactive to HLA‐DQ molecules expressed on mouse L cell transfectants

“…On the other hand, the DR2(DRB5*0102) gene derived from the HLA-Dw12 haplotype was thought to be equivalent to DR4(DRB1*0405) in terms of expression level of mRNA and the mRNA of DR2(DRB5*0102) was twice as much as that of DR2(DRB1*1502) [30]. Using HLA-DR or -DQ transfected B cell lines, Merkenschlager et al [31] have just reported a similar observation that HLA-DQ recognition in MLR may occur more frequently than considered from previous antibody blocking studies.…”