Pellegrino Ma

Expression of Ia-like antigens in normal human nonlymphoid tissues.

Recent results have demonstrated that Ia-like antigen expression in animal tissues is not restricted to cells associated with immune functions. Whether this phenomenon occurs in normal human tissues has been investigated in this study by indirect immunofluorescence on cryostat sections using monoclonal antibodies to framework determinants of Ia-like antigens. The results of this study show that la-like antigens are expressed on several normal human tissues of different embryonic origin. These include the epithelium of the gastrointestinal tract, urinary bladder, bronchial glands, thymic reticuloepithelial cells (entodermie origin), epithelium of mammary gland, acinar cells of parotid, astrocytes (ectodermic origin), alveolar macrophages, Kupffer cells, glomerular and peritubular renal endothelium, endometrium, and Langerhans cells (mesodermic origin).

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.

Higher cytolytic efficiency of an IgG2α than of an IgG1 monoclonal antibody reacting with the same (or spatially close) determinant on a human high-molecular-weight melanoma-associated antigen

Abstract Serological and immunochemical assays showed that the monoclonal antibody (MoAb) 225.28S, an IgG2α, and the MoAb 653.40S, an IgG1, react with the same (or spatially close) antigenic determinant expressed on a set of molecules carrying a high-molecular-weight human melanoma-associated antigen. Neither monoclonal antibody mediates complement-dependent lysis of cultured melanoma cells, but both of them specifically mediate lysis of target cells in an antiglobulin cytotoxic assay and in an antibody-dependent cell-mediated cytotoxicity (ADCC) assay. In the latter two assays the IgG2α displays a higher lytic activity than the IgG1. The differential lytic activity of the IgG2α and IgG1 monoclonal antibodies was detected also when the sensitivity of the ADCC assay was increased either by boosting the cytolytic activity of the effector cells or by enhancing the susceptibility to lysis of target cells.

Immunogenicity of HLA antigens purified from serum.

The immunogenic properties of HLA-A9 antigens isolated from serum have been evaluated. A9 antigens at various stages of purification can elicit the formation of cytotoxic antibodies which become operationally specific to A9 either after absorption of the xenoantisera with cultured human lymphoid cells or human red blood cells, or after dilution of xenoantisera with human serum. A9 xenoantisera do no affect mixed lymphocyte reactions between allogeneic lymphocytes carrying A9, suggesting that coating of antigens of the A locus does not impair the functional activity of lymphocytes in the mixed lymphocyte reaction.

Humoral sensitization in parous women: cytotoxic antibodies to non HL-A antigens.

SUMMARY From sera of parous women, we selected 100 samples that lacked cytotoxic antibodies to human peripheral lymphocytes from at least 80 unrelated persons. These sera were then reacted with a panel of 17 cultured human lymphoid cells in the complement-dependent cytotoxic test. Forty-six sera contained cytotoxic antibodies apparently directed to an antigenic system distinct from HL-A antigens, and other known cell surface markers. Rabbit serum was the most efficient source of complement with these cytotoxic antibodies which did not appear to be directed to tumor associated antigens: in fact, no lysis of melanoma cells or leukemic cells could be detected. Ten specificities could be identified which were represented on the cultured human lymphoid cells in various combinations. It is suggested that antigens detected by this approach may be similar to the Ia antigens of the mouse.

Solubilization of fetal HL-A antigens. A preliminary report.

SUMMARY Water-soluble substances bearing HL-A antigenic determinants were extracted from the spleen, lung, liver, and kidney of 3-, 4-, and 5½ -month fetuses. These substances inhibited alloantisera in a pattern consistent with the phenotype of the antigen donor. There were significant differentials in the HL-A antigens which were solubilized from various tissues. Fetal kidney was the best source for the solubilization of HL-A antigens by sonic energy.

Ontogeny of human Ia antigens

Abstract Indirect immunofluorescence (IIP) staining of tissues from human fetuses (ages ranging from 8 to 32 weeks of intrauterine life) with monoclonal antibodies (MoAb) to monomorphic determinants of Ia antigens and HLA-A,B,C antigens has shown that both types of antigens are already detectable in tissues of 8-week-old fetuses. Ia antigens and HLA-A,B,C antigens reach their almost-complete tissue distribution after 32 and 24 weeks of intrauterine life, respectively. The structure of Ia antigens synthesized by fetal thymus cells is similar to that of B-lymphoid cell-derived Ia antigens. Ia antigen-bearing thymic fetal cells can stimulate allogeneic lymphocytes in mixed lymphocyte reactions (MLRs). These reactions are blocked by monoclonal antibodies to monomorphic determinants of human Ia antigens and of HLA-A,B, antigens.

A quantitative study of cross reactivity in the HL-A system with human cultured lymphoid cells and soluble HL-A antigens.

SUMMARY Cross reactivity in the HL-A system has been evaluated quantitatively by utilizing human cultured lymphoid cells and soluble HL-A antigens in cross absorption and cross inhibition assays. Most of the cross reactions among different HL-A specificities determined with platelets or peripheral lymphocytes were confirmed in this study. Some cultured lymphoid cells or soluble HL-A antigens possessing a cross reacting specificity cross absorbed a certain anti-HL-A antiserum, whereas others with the same specificity did not. The number of cells required to absorb cytotoxic HL-A alloantisera directed against cross reacting specificities is significantly greater than that necessary to absorb alloantisera directed against HL-A determinants present on the cell surface. This observation suggests that relatively small numbers of available antigenic determinants react with the cross reacting antibodies. The differential absorbing capacity of different cultured cell lines for the same cross reacting HL-A alloantibodies suggests a variability in the cell surface expression of cross reacting HL-A determinants.

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.

Utilization of cultured human lymphoid cells for detection of humoral sensitization in prospective recipients of kidney transplants.

Prospective recipients of kidney transplants were tested for lymphocytotoxicity; from these we selected 102 sera that lacked cytotoxic antibodies against peripheral lymphocytes from at least 80 unrelated subjects. To detect humoral sensitization, we then reacted these with 17 cultured human lymphoid cell lines having different HL-A phenotypes. Cytotoxic antibodies reacting with these cultured cells were now detected in some of the sera. These antibodies were not directed against HL-A antigens, yet mediated lysis of target cells in the presence of rabbit but not of human or guinea pig complement. Furthermore, they activated the classical pathway of the rabbit complement system. Later, a significant association was found between occurrence of cytotoxic antibodies and rejection of the transplant. Thus, cultured human lymphoid cells, because of their great susceptibility to complement-mediated lysis, appear to be useful in detecting humoral sensitization in candidates for kidney grafts.