Antibody-induced association between discrete regions of HLA class I and II antigens

The anti-HLA-DR + DP monoclonal antibody (MoAb) CR11-462 was unexpectedly found to cross-inhibit the binding to B lymphoid cells of the anti-HLA Class I MoAb CR10-215 and CR11-115. The latter two antibodies recognized the same or spatially close antigenic determinant. The cross-blocking of anti-HLA Class I MoAb CR10-215 and CR11-115 by MoAb CR11-462 reflects neither its contamination by anti-HLA Class I antibodies nor its cross-reactivity with HLA Class I antigens. On the other hand, the cross-blocking appears to reflect redistribution of HLA Class II antigens by the MoAb CR11-462, since the MoAb CR10-215 and CR11-115 are not susceptible to blocking when lymphoid cells are treated with 0.025% glutaraldehyde or are coated with Fab' fragments of the MoAb CR11-462. Furthermore, immunoprecipitates from B lymphoid cells preincubated with the MoAb CR11-462 before solubilization contain HLA Class I antigens. Therefore, these results have shown for the first time an antibody-induced association between discrete regions of HLA Class I and Class II antigens on the membrane of B lymphoid cells.

A double determinant immunoassay for HLA class I typing using serum as an antigen source

We have applied a double determinant immunoassay (DDIA) to HLA-A2,A28, and B13 typing, using serum as an antigen source. The results obtained show a correlation of 96% (B13) and 89.1% (A2,A28) with the results obtained by conventional HLA typing. Furthermore, the results obtained were highly reproducible, since testing of 18 sera on two occasions gave concordant results with all samples tested. The variation in the content of HLA-A2 antigens in sera taken at different times from a given donor was less than 5%. A sevenfold variation was found in the serum level of HLA-A2,A28 antigens: the highest level was found in the sera from HLA-A2,A28 donors and in decreasing order in HLA-A2 homozygous, HLA-A28 homozygous, HLA-A2 heterozygous, and HLA-A28 heterozygous donors. The results of this study indicate that the DDIA is a sensitive, simple, and reproducible procedure for HLA class I typing. The DDIA offers the following advantages in comparison with the conventional lymphocytotoxic assay: it provides information not only about the expression of a given alloantigen, but also about its level; it does not require viable cells, thus facilitating retrospective studies and typing of leucopenic patients; it eliminates variability of results caused by abnormal susceptibility of target cells to complement-dependent lysis.

Evidence for an activated subpopulation of T8-bearing cells in male homosexuals with lymphadenopathy

Data are presented that male homosexuals with chronic lymphadenopathy and reduced numbers of T4-antigen-bearing cells have an increased incidence of activated T8-antigen-bearing cells. Evidence suggesting an increase in activated T cells in these subjects includes an increase in incidence of T10-antigen-bearing cells, an increase in Ia-bearing T cells and an increase in the intensity of staining of a fraction of the T8-antigen-bearing cells with fluorescein-labeled OKT8 monoclonal antibody. It was shown by double staining that most of the Ia-bearing T cells also bore the T8 marker. The heterogeneity of the Ia, assayed by reactivity with several monoclonal anti-Ia antibodies which detect different epitopes on the Ia molecule, was comparable in lymphadenopathy subjects and controls.

Human helper-T-cell function does not require T4 antigen expression

The relationship between immunoregulatory T-cell function and the expression of T-cell subset-specific differentiation antigens was examined using a phenotypically anomalous human T-cell line (TCL), termed H-1. H-1 cells were found to express T11, extremely high levels of T3, but no T4 nor T8 antigen. Despite their lack of T4 antigen expression, H-1 cells could be activated by coculture with pokeweed mitogen (PWM), anti-T3 antibody, or autologous B cells to provide potent help for B-cell differentiation into plaque-forming cells (PFC). In contrast, H-1 cells did not suppress the PFC response triggered by PWM-activated T4+ cells. These results demonstrate that the expression of the T-cell subclass-specific differentiation antigen, T4, is not required for a T cell to become activated and to implement the program for helper function. In addition, enhanced expression of T3 on the T4-, T8-, H-1 cell surface may reflect a compensatory upregulation of the T3/Ti receptor complex on T cells which are deficient in these nonpolymorphic associative recognition structures.

T cell proliferation induced by anti-self-I-A-specific T cell hybridomas. Evidence of a T cell network

Allo-I-A-reactive T cell hybridomas were generated from MLR-activated lymphoblasts. Cloned hybridomas T1.203, T1.321, and T1.426 were stimulated by I-Ab determinants, as shown by their ability to secrete IL-2 in response to a panel of MHC-recombinant mice. T2.146, T2.205, and T3.116 were found to be specific for I-Ak determinants using a similar panel of MHC-recombinant mice. Inhibition of IL-2 secretion by anti-I-A mAb confirmed these data. Some I-Ab-specific hybrids stimulated the proliferation of T cells from C57BL/6 (H-2b) mice. Similarly, some I-Ak-specific hybrids stimulated the proliferation of T cells from C3H/HeJ (H-2k) mice. These hybrids expressed no detectable surface I-A, and stimulation of T cells was not inhibited by anti-I-A mAb. These results are consistent with the hypothesis that normal mice possess a population of T cells responsive to idiotypic determinants on anti-MHC class II T cell receptors.

Requirements for T cell activation by OKT3 monoclonal antibody: role of modulation of T3 molecules and interleukin 1

The requirements for activation of human peripheral blood T cells by the mitogenic monoclonal antibody OKT3 were examined. OKT3 binds to a T cell molecule, T3, associated with the T cell antigen receptor and involved in T cell activation. Activation of T cells by OKT3 requires signals provided by accessory cells and is IL 2 dependent. In the presence of accessory cells, OKT3 induces loss of T3 molecules from the cell surface, production of IL 2, expression of IL 2 receptors, and proliferation. Modulation of T3 molecules by OKT3 can be induced in the absence of accessory cells with anti-mouse IgG. These T cells, however, are not induced to express IL 2 receptors or secrete IL 2. The addition of IL 1 induces expression of IL 2 receptors, but does not induce IL 2 secretion or proliferation. Thus, peripheral blood T cells appear to have different requirements for activation compared with antigen-specific T cell clones that can be induced to produce IL 2 when stimulated with OKT3 and IL 1. Expression of IL 2 receptors does not require modulation of T3 molecules, because the binding of OKT3 to T cells in the presence of IL 1 alone is sufficient to induce IL 2 receptor expression. The results suggest that IL 2 secretion depends on cross-linking and modulation of T3 molecules, and additional, as yet undefined, accessory cell signals. The expression of IL 2 receptors and proliferation of T cells can be induced in the absence of these signals when exogenous IL 2 is provided.

Requirements for T cell activation by OKT3 monoclonal antibody: role of modulation of T3 molecules and interleukin 1

The requirements for activation of human peripheral blood T cells by the mitogenic monoclonal antibody OKT3 were examined. OKT3 binds to a T cell molecule, T3, associated with the T cell antigen receptor and involved in T cell activation. Activation of T cells by OKT3 requires signals provided by accessory cells and is IL 2 dependent. In the presence of accessory cells, OKT3 induces loss of T3 molecules from the cell surface, production of IL 2, expression of IL 2 receptors, and proliferation. Modulation of T3 molecules by OKT3 can be induced in the absence of accessory cells with anti-mouse IgG. These T cells, however, are not induced to express IL 2 receptors or secrete IL 2. The addition of IL 1 induces expression of IL 2 receptors, but does not induce IL 2 secretion or proliferation. Thus, peripheral blood T cells appear to have different requirements for activation compared with antigen-specific T cell clones that can be induced to produce IL 2 when stimulated with OKT3 and IL 1. Expression of IL 2 receptors does not require modulation of T3 molecules, because the binding of OKT3 to T cells in the presence of IL 1 alone is sufficient to induce IL 2 receptor expression. The results suggest that IL 2 secretion depends on cross-linking and modulation of T3 molecules, and additional, as yet undefined, accessory cell signals. The expression of IL 2 receptors and proliferation of T cells can be induced in the absence of these signals when exogenous IL 2 is provided.

Heterogeneity of human peripheral blood mononuclear cells detected by monoclonal antibodies to monomorphic determinants of human Ia antigens

The reactivity patterns of several monoclonal antibodies specific for monomorphic determinants of human Ia antigens were studied using flow cytometric techniques. We observed differential reactivity of these antibodies with human lymphoid cell lines, normal fresh human mononuclear cells, and lymphoblasts from PHA-activated cultures. The molecular heterogeneity of Ia antigens previously identified with immunochemical techniques was accompanied by heterogeneity of cell surface expression as identified by an immunofluorescent probe. The determinants identified by these anti-Ia monoclonal antibodies may provide useful markers in the isolation of cellular subpopulations responsive in the immune system.

Reactivity patterns with HLA-A2 variants indicate lack of identity between determinants defined by monoclonal antibodies and cytotoxic-T-cell clones

The anti-HLA-A2 monoclonal antibodies (MoAb) CR11-351 and 4B inhibit the binding of each other to HLA-A2 lymphoid cells and block the cytotoxicity of the anti-HLA-A2 cytotoxic-T-cell clone R32. The blocking does not reflect reactivity of the MoAb CR11-351 and 4B and of the cytotoxic-T-cell clone R32 with the same determinant, since they display differential reactivity with four HLA-A2 variants which carry amino acid substitutions at different positions. These results show for the first time in the human system that Class I HLA variants represent useful reagents to compare the fine specificities of monoclonal antibodies and T-cell clones. Furthermore our data suggest that T-cell recognition depends upon the tertiary structure of the antigen.

Immunohistochemical analysis of malignant melanomas and nevocellular nevi with monoclonal antibodies to distinct monomorphic determinants of HLA antigens

Using an indirect immunoperoxidase technique, 20 nevocellular nevi, 5 dysplastic nevi, 14 primary cutaneous melanomas, and 24 metastatic melanomas were tested with a panel of monoclonal antibodies to monomorphic determinants of Class I (HLA-A,B,C) and Class II (la-like) major histocompatibility complex antigens. Class I HLA and beta 2-microglobulins were not detected on the majority of nevus cells but were expressed by 3 of 5 dysplastic nevi, by the majority of tumor cells in 12 of 14 primary cutaneous melanomas, and in 13 of 24 metastases. The different expression of Class I HLA and beta 2-microglobulins in primary and metastatic lesions suggests that loss of these antigens may be associated with progression of malignancy. Class II HLA were not detected in common nevi but were locally present in 1 of 5 dysplastic nevi, 7 of 14 cases of primary cutaneous melanoma, and all 24 cases of metastatic lesions tested. These findings suggest that increase in Class II HLA expression may be associated with progression of malignancy. The staining patterns obtained with monoclonal antibodies to distinct determinants of Class I HLA and Class II HLA were superimposable within each type of antigen. Therefore, the discrepancies in the literature about the expression of histocompatibility antigens by lesions of melanocytic origin are not likely to reflect the different specificity of the antibodies used by the various investigators.

Analysis of the repertoire of anti-HLA antibodies with anti-idiotypes to a murine anti-HLA-A2,A28 monoclonal antibody

Xenoantibodies to idiotypes of the anti-HLA-A2,A28 MoAb CR11 -351 were isolated from an antiserum raised in rabbit #81 by immunizations with purified MoAb CR11 -351. The purification procedure involved absorption with insolubilized mouse immunoglobulins and monoclonal antibodies and affinity chromatography on insolubilized MoAb CR11 -351. Two antibody populations were identified in the xenoantibody preparation #81: one recognizes a recurrent idiotope expressed by the MoAb CR10 -215, CR10 -402, Q1/28, Q6 /64, and 6/31 to monomorphic determinants of HLA-A,B antigens and by the MoAb CR10 -343, CR11 -462, and Q5/6 to human Ia antigens. The other antibody population recognizes a private idiotope. Neither idiotope was detected on the anti-HLA-A2,A28 variant (A28) MoAbs BB7 .2, MA2 .2, and PA2.1, on the anti-HLA-A2,B17 MoAb MA2 .1 and on antibody populations in conventional anti-HLA-A2,A28 antisera. The idiotopes were also not detected on the anti-HLA-A2,A28 MoAb A2,A28 M1 which recognizes a determinant spatially close to that identified by the MoAb CR11 -351. The idiotope(s) recognized by the xenoantibodies #81 may be located in the combining site of the MoAb CR11 -351, since its incubation with the anti-idiotype antibodies specifically blocks the reactivity with lymphoid cells with the appropriate HLA phenotype.

Complement-dependent killing of human hematopoietic progenitor cells with noncomplement-fixing monoclonal antibodies in an antiglobulin assay

A complement (C)-dependent antiglobulin assay was utilized to determine the reactivity of non-C-fixing monoclonal antibodies (MoAb) with human granulocyte-macrophage progenitor cells (CFU-GM). The variables of the assay were analyzed with non-C-fixing MoAb against Ia antigens, including CR11-462, which recognizes the same (or spatially close) determinant identified by the C-fixing anti-Ia MoAb Q5/13. The sensitivity of the antiglobulin assay was influenced by dilutions of anti-mouse Ig xenoantiserum and of rabbit C. Five non-C-fixing MoAb to Ia antigens, seven non-C-fixing MoAb to HLA-A,B antigens, and one non-C-fixing MoAb to beta 2-microglobulin induced marked inhibition of human CFU-GM in the antiglobulin assay. The activity of non-C-fixing MoAb in the antiglobulin assay was comparable to that of C-fixing anti-Ia and anti-HLA-A,B MoAb in the standard cytotoxicity assay. In addition, the cytotoxic effect of dilute C-fixing anti-Ia MoAb was enhanced when the antiglobulin technique was employed. The results of this study indicate that the antiglobulin assay is a rapid and simple technique for the characterization of antigens on human hematopoietic progenitors. Our data also indicate that Ia antigens are expressed on most CFU-GM and that the conflicting results in the literature (that is, those suggesting that Ia antigens are expressed on a smaller proportion of CFU-GM) may reflect differences in the cytolytic activity of the MoAb and rabbit C used.

HLA class I specific T lymphocyte clones with dual alloreactive functions

Four human T lymphocyte clones exhibiting proliferative responses to class I HLA antigens were isolated from an in vitro mixed lymphocyte culture (MLC). Three clones expressed the Leu-2+3- phenotype and demonstrated proliferation in response to HLA-B8, while the fourth clone expressed the Leu-2-3+ phenotype and proliferated in response to HLA-A2. These clones were also cytotoxic towards cells bearing the same target antigens. Blocking studies utilizing monoclonal antibodies demonstrated that proliferation was triggered by determinants on the class I molecule itself, and these determinants appear to be spatially close to those which determine serologic allospecificity. These findings support the concept that the class I molecules themselves are the weak MLC stimulating determinants previously mapped to the HLA-A and B regions of the major histocompatibility complex.

Inhibitory effect of a low dose of prednisone on PHA-induced Ia antigen expression by human T cells and on proliferation of T cells stimulated with autologous PHA-T cells

Administration of a small dose of prednisone markedly reduced (1) the PHA-induced expression of Ia antigens by T cells, (2) the stimulatory activity of Ia antigen-bearing T cells in autologous and allogeneic mixed lymphocyte reactions (MLRs), and (3) the proliferative response of T cells stimulated with autologous PHA-activated T cells or autologous or allogeneic non-T cells. The inhibitory effects of prednisone are reversible and are not detectable on T cells isolated from blood drawn 24 hr following prednisone administration. The kinetics of the prednisone-mediated inhibition of MLRs with autologous PHA-T cells is different from that of MLRs with autologous non-T cells. These data in conjunction with the information available in the literature suggest that the mechanisms underlying these two types of autologous MLRs are different.

Role of distinct domains of Ia antigens in autologous and allogeneic mixed lymphocyte reactions

Murine monoclonal antibodies (MoAb) to distinct determinants of human Ia antigens and low doses of prednisone induce different effects on the autologous mixed lymphocyte reaction (MLR), stimulated by PHA-T cells or by non-T cells, and on allogeneic MLRs. These results suggest that distinct domains of Ia antigens and/or mechanisms are involved in these types of MLRs.

Antigenic heterogeneity of surgically removed primary and autologous metastatic human melanoma lesions

The antigenic heterogeneity of primary and metastatic lesions surgically removed from nine patients with nodular melanoma was investigated by using monoclonal antibodies to HLA-A, B antigens, to beta 2-microglobulin, to Ia antigens, and to melanoma-associated antigens (MAA). The latter include three types of membrane-bound MAA and a cytoplasmic MAA. In spite of an homogeneous morphologic appearance, multiple lesions removed from the same patient differed significantly in their reactivity with the panel of monoclonal antibodies in indirect immunofluorescence test. The extent of antigenic heterogeneity did not correlate with melanin synthesis, site of origin of the primary tumor, site of metastatic foci, or treatment, but was less marked in patients carrying the primary tumor. The antigenic heterogeneity of multiple lesions removed from one patient and the independent expression of the various types of MAA investigated suggest that combinations of monoclonal antibodies to MAA may be more effective than single antibodies for radioimaging and immunotherapy.

Human T lymphocytes in aging and malignancy: abnormalities in PHA-induced Ia antigen expression and in functional activity in autologous and allogeneic MLR

T lymphocytes from patients with solid tumors and from aged donors are abnormal in their expression of Ia antigens following in vitro stimulation with phytohemagglutinin (PHA). Ia antigens were not detected on PHA-activated T lymphocytes from 15 of 27 patients with solid tumors. The abnormality in T lymphocytes from 25 donors older than 60 years was evidenced by a reduction in the percentage of T cells acquiring Ia antigens following stimulation with suboptimal amounts of PHA and by a delayed appearance of those antigens. In both groups of donors the defect in Ia antigen expression by PHA-activated T cells did not correlate with the reduced [3H]thymidine uptake. PHA-activated T cells from aged donors and from patients with solid tumors were poorly stimulatory in autologous and allogenic mixed lymphocyte reactions. Furthermore, T lymphocytes from these two groups of donors displayed a reduced proliferative response to autologous non-T cells, but a normal proliferative response to allogeneic PHA-activated T cells and to non-T cells from control subjects.

Antigenic heterogeneity of surgically removed primary and autologous metastatic human melanoma lesions

The antigenic heterogeneity of primary and metastatic lesions surgically removed from nine patients with nodular melanoma was investigated by using monoclonal antibodies to HLA-A, B antigens, to beta 2-microglobulin, to Ia antigens, and to melanoma-associated antigens (MAA). The latter include three types of membrane-bound MAA and a cytoplasmic MAA. In spite of an homogeneous morphologic appearance, multiple lesions removed from the same patient differed significantly in their reactivity with the panel of monoclonal antibodies in indirect immunofluorescence test. The extent of antigenic heterogeneity did not correlate with melanin synthesis, site of origin of the primary tumor, site of metastatic foci, or treatment, but was less marked in patients carrying the primary tumor. The antigenic heterogeneity of multiple lesions removed from one patient and the independent expression of the various types of MAA investigated suggest that combinations of monoclonal antibodies to MAA may be more effective than single antibodies for radioimaging and immunotherapy.