Fine specificity of human HLA-B7-specific cytotoxic T-lymphocyte clones. I. Identification of HLA-B7 subtypes and histotopes of the HLA-B7 cross-reacting group.

Three HLA-B7-specific cytotoxic T lymphocyte (CTL) clones are described. Their fine specificity is examined by extensive panel and family studies. Four CTL-defined subtypes of HLA-B7 could be found: HLA-B7.1, -B7.2, -B7.3, and -B7.4. Biochemical evidence was obtained in one-dimension isoelectric focusing for only two subtypes. The estimated subtype frequencies in the Caucasian population are presented. Furthermore, a linkage disequilibrium between HLA-A29 and HLA-B7.3 is suggested. The CTL clones exerted distinct "extra-reactivities", i.e., lysis of some non-B7 target cells. These extra reactivities could be assigned to the cross-reacting group of HLA-B7.

Identification of new B27 subtypes (B27C and B27D) prevalent in oriental populations.

With the aid of alloreactive cytotoxic T lymphocytes, three subtypes of HLA-B27 can be defined: B27W, B27K, and B27C (non-B27W and non-B27K). The B27C subtype can be distinguished by 1D-IEF, is not recognized by B27W- or B27K-restricted influenza-A-specific cytotoxic T lymphocytes, and is prevalent in Oriental populations. Preliminary data indicate that the various B27 subtypes (W, K, C) are in different linkage disequilibria with HLA-C antigens. A fourth subtype of B27 (non-B27W and non-B27K), designated as B27D, was detected by 1D-IEF. (See accompanying paper by Neefjes et al.) The finding of four B27 subtypes indicates that the serologically defined B27 antigen comprises a family of various, strongly cross-reactive class-I molecules.

Specificity of anti-HLA-B27 cytotoxic T lymphocytes.

Sub-types of HLA-B27 were detected by cytotoxic T lymphocytes (CTL) generated between HLA-A, -B- and -C-identical B27-positive individuals. We now report the specificity of six independent CTL's generated by mixed lymphocyte culture (MLC) of HLA-A, -B and -C serologically identical B27-positive responder and stimulator cells. Three CTL's recognize one sub-type, and three the other. The combined reactivity of all CTL's allows unequivocal "typing" of B27-positive cells for the two different sub-types B27K and B27W. The specificity of two CTL's was analysed by cold-target inhibition. The results indicate that (1) no further sub-types of HLA-B27 can be detected by the CTL's raised in these combinations; (2) the majority of the CTL's is directed against the B27 antigens; and (3) "extra reactions" on B27-negative cells are caused by a subset(s) of CTL's recognizing unknown antigens shared between stimulator and target cells. CTL's raised by stimulation of HLA-B27-negative responder cells with B27-positive cells of either sub-type lysed all B27-positive target cells indiscriminately. In cold-target inhibition, however, B27-positive cells, carrying the sub-type of B27 different from that of the stimulator, could not inhibit the lysis of cells bearing the stimulator sub-type of B27. This indicates the activation, in B27-negative responders, of at least two different groups of CTL clones, one directed against shared determinants of HLA-B27, and one against the HLA-B27 sub-type. Heterogeneity of the HLA-B27 antigen may have implications for studies on the well-known association between this antigen and various diseases.

Immunoglobulin production in human mixed lymphocyte cultures: implications for co-cultures of cells from patients and healthy donors.

When human peripheral blood lymphocytes (PBL) are cultured in the presence of irradiated allogeneic lymphocytes, the resulting mixed lymphocyte reaction (MLR) leads to the secretion into the supernatant of substantial amounts of IgM and IgG, derived from nonirradiated responder B lymphocytes. Our data indicate that stimulation to Ig production by responder B cells may result from different types of interactions. First, B cells and monocytes among the irradiated stimulator cells activate T cells in the responder population, which in turn trigger responder B cells to produce Ig; second, "responder" B cells activate irradiated "stimulator" T cells, leading to a "helper" signal, back to the responder B cells and leading to Ig production. The latter system is radiosensitive, because allogeneic T cells, irradiated at a dose of 4000 rad or more, failed to induce Ig production by responder B cells. In some combinations of human allogeneic lymphocytes, the co-culture of the cells leads to inhibition of Ig production, both in the presence and in the absence of PWM. Thus, co-culture of allogeneic cells may cause "positive" as well as "negative" allogeneic effects. The implications of these findings for the interpretation of co-cultures that are aimed at establishing defects in lymphocytes from patients with, for example, immunodeficiencies, who fail to produce Ig in the presence of PWM are discussed.