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

An Anti-C1s Monoclonal, TNT003, Inhibits Complement Activation Induced by Antibodies Against HLA

Antibody-mediated rejection (AMR) of solid organ transplants (SOT) is characterized by damage triggered by donor-specific antibodies (DSA) binding donor Class I and II HLA (HLA-I and HLA-II) expressed on endothelial cells. While F(ab')2 portions of DSA cause cellular activation and proliferation, Fc regions activate the classical complement cascade, resulting in complement deposition and leukocyte recruitment, both hallmark features of AMR. We characterized the ability of an anti-C1s monoclonal antibody, TNT003, to inhibit HLA antibody (HLA-Ab)-induced complement activation. Complement deposition induced by HLA-Ab was evaluated using novel cell- and bead-based assays. Human aortic endothelial cells (HAEC) were cultured with HLA-Ab and human complement; production of activated complement proteins was measured by flow cytometry. Additionally, C3d deposition was measured on single antigen beads (SAB) mixed with HLA-Ab and human complement. TNT003 inhibited HLA-Ab mediated complement deposition on HAEC in a concentration-dependent manner; C3a, C4a and C5a anaphylatoxin production was also diminished by TNT003. Finally, TNT003 blocked C3d deposition induced by Class I (HLAI-Ab)- and Class II (HLAII-Ab)-specific antibodies on SAB. These data suggest TNT003 may be useful for modulating the effects of DSA, as TNT003 inhibits complement deposition and split product formation generated by HLA-I/II-Ab in vitro.

An antiglobulin microcytotoxicity assay to analyze non-complement fixing monoclonal antibodies to human histocompatibility antigens

An antiglobulin microcytotoxicity assay has been used to analyze non-complement fixing monoclonal antibodies to human histocompatibility antigens. The assay utilizes methodology similar to that of the widely used microcytotoxicity assay for HLA typing, requires low numbers of target cells and is suitable to test large numbers of samples. The sensitivity of the assay is influenced by the anti-mouse Ig antiserum used, by the sequence of addition of the various reagents and by the incubation time. The assay is suitable to screen supernatants of clones derived from hybridization experiments and to characterize the serological specificity of anti-HLA monoclonal antibodies.

Ultrastructural alterations in human lymphoblastoid B cell lines treated with tunicamycin

The ultrastructure of three human lymphoblastoid B cell lines, Raji, RPMI 4098, and WIL-2, was analyzed after the cells were incubated with tunicamycin, and antibiotic that selectively inhibits N-linked glycosylation of macromolecules. After a 24-hour exposure to 1.0 microgram/ml of tunicamycin, the lymphocytes lose their microvilli and become smooth spheres or develop a few blebs. Also, the cells show a dilation of the endoplasmic reticulum and an increase in myelin figures resulting from intracellular membrane accumulation, possibly lysosomal in origin. These ultrastructural alterations are similar to those observed in Tay-Sachs, Fabrey's, and Gaucher's diseases, Type II pneumocytes in viral pneumonitis, certain lysosomal storage diseases, and in aging fibroblasts. Therefore, tunicamycin-treated cells may be a useful model in the correlation of altered ultrastructural pattern in membrane flow with the etiology of certain diseases.

The monoclonal xenoantibody Q6/64 recognizes a determinant expressed by certain gene products of the A and B loci of the HLA region

A combination of serological (cytotoxicity, binding assay, lysostrip) and immunochemical (indirect immunoprecipitation, sequential immunoprecipitation, two-dimensional gel electrophoresis) assays have shown that the monoclonal antibodies Q6/64 recognizes an antigenic determinant which is expressed by certain gene products of the A and b loci of the HLA region. The determinant identified by Q6/64 is spatially close to those which define the serological polymorphism of the HLA-A, B, C antigenic system. The results presented in this study in conjunction which those recently published by other investigators indicate that sharing of determinants among HLA-A and -B allospecificities is more frequent than originally assumed on the basis of the cross-reactivity pattern obtained with alloantisera. This conclusion is in agreement with the high degree of homology in the primary amino-acid sequence of A and B allospecificities.

Cross-reactivity between human and murine lymphocyte antigens. IV. Reactivity of H-2 alloantisera with HLA-A, B antigens

The anti-H-2 alloantiserum D-32 [(B10.A(2R) x C3H.SW) anti-C3H] is cytolytic to human lymphocytes. Fab2 blocking assays, indirect immunoprecipitation and sequential immunoprecipitation experiments showed that the anti-H-2 alloantiserum D-32 recognizes antigenic determinants which are expressed on the heavy chain of subpopulations of HLA-A, B antigens. These determinants are different from those defining the serological polymorphism of the HLA-A, B, C system, are the same as or spatially close to those recognized by the anti-HLA-A, B monoclonal antibody Q6/64 and are expressed on rabbit, rat or guinea pig lymphocytes.

Serological, functional, and immunochemical characterization of a monoclonal antibody (MoAb Q2/70) to human Ia-like antigens

Serological and immunochemical studies showed that monoclonal antibody Q2/70 (MoAb Q2/70), produced by the hybridoma technique, is specific for human Ia-like antigens. This antibody recognizes an antigenic determinant which is different from those defining the serologic polymorphism of Ia-like antigens, and is expressed on subsets of human Ia-like molecules and on lymphoid cells from other species. MoAb Q2/70 inhibits unidirectional MLRs* between allogenic human lymphocytes, but not between murine and human lymphocytes. In ADCC* assays. MoAb Q2/70 mediates lysis of cultured human B lymphoid cells RPMI 4098, effected by murine splenocytes. The antibody is suitable to isolate immunologically functional B lymphocytes from human peripheral blood.

Lymphocytotoxic antibodies in systemic lupus erythematosus patients and their relatives: reactivity with the HLA antigenic molecular complex

Lymphocytotoxic activity of sera from systemic lupus erythematosus (SLE) patients and their families was inhibited by 50% or more by preincubation of target cells with Fab2 fragments of xenoantisera against beta 2 microglobulin or the heavy chain of the HLA-A,B,C antigenic molecular complex. An antiHLA-DR xenoantiserum had less blocking effect on peripheral blood mononuclear cells but was effective at blocking reactivity of these sera against cultured B lymphoid cell lines. The repertoire of specificities in family members' sera differed from each other and their respective proband with respect to their reactions with cultured lymphoid cell lines. These data indicate that lymphocytotoxic antibodies (LCA) found in most patients with SLE and some of their relatives include a subpopulation with specificity for determinants present on major histocompatibility gene products. They also suggest that LCA in relatives represent a defect in immune regulation which allows expression of existing autoimmune potentials rather than immunization with a single "lupus" antigen.

Detection of human histocompatibility (HLA) antigens with an indirect rosette microassay

An indirect rosette assay which utilizes erythrocytes coupled with purified antiimmunoglobulin (Ig) antibodies was modified into a microassay for detecting HLA allo-and xenoantibodies. The test, which is performed in microtiter plates, is specific, reproducible and can handle large numbers of samples. As an inhibition assay the test can detect HLA antibodies even if mixed with antibodies to other cell surface structures. The rosette microassay is at least 10 times more sensitive than the complement-dependent microcytotoxic test and can use target cells which exhibit low viability or abnormal susceptibility to lysis.

Cytotoxic antibodies to cultured human lymphoid cells in polytransfused thrombocytopenic patients: association with reduced survival of allogeneic transfused platelets

Four out of 8 thrombocytopenic patients without detectable cytotoxic antibodies to human peripheral lymphocytes contained cytotoxic antibodies to cultured human lymphoid cells. The presence of such antibodies was associated with reduced survival of infused allogeneic platelets in these patients. The antibodies reacted in a distinct fashion with a panel of cultured human lymphoid cells and are directed to B cell antigens. Cytotoxic antibodies to cultured human lymphoid cells did not react in vitro with platelets suggesting that the antibodies play no significant role in the accelerated destruction of infused allogeneic platelets, although their presence predicts it. Therefore, screening of sera with cultured human lymphoid cells appears to be a useful test in addition to those now used to select patients for transfusion of allogeneic platelets. Sera from polytransfused patients without cytotoxic antibodies to peripheral lymphocytes may be a useful source of antibodies to B cell antigens.

Expression of C4 on human lymphoid cells and possible involvement in immune recognition phenomena

Immunochemical studies revealed the presence of the fourth component of complement (C4) on surfaces of human lymphoid cells. Antiserums to C4 inhibited the mixed lymphocyte reaction and the mitogenic response to phytohemagglutinin, suggesting a role for membrane-associated C4 in the afferent phase of immune recognition phenomena.