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Biomedical subjects

T Mohanakumar

Publications and source records attributed to T Mohanakumar.

At least 235 records · Page 13Linked to original sources
PubMed1983

Properties of two monoclonal antibodies directed against the Fc and Fab' regions of rat IgE.

Hybridoma antibodies directed against the Fc and Fab portions of rat IgE were produced by immunizing BALB/c mice with rat IgE and fusing the spleen cells with the nonsecreting plasmacytoma P3/X63Ag8.653. Two of the antibodies, designated as A2 and B5, were extensively characterized. Competitive binding experiments using rat IgE from the IR 162 and IR2 immunocytomas and rat IgG indicated that both A2 and B5 were epsilon-chain specific and not anti-idiotype. A2 also exhibited some cross-reactivity with mouse IgE. When IgE was treated with chymotrypsin so as to produce both F(ab')2 and Fab fragments, the enzyme-treated IgE retained reactivity with B5, but the reactivity to A2 was lost. Heat denaturation of IgE at 56 degrees C resulted in a progressive loss of reactivity of the IgE for both A2 and the Fc receptor on rat basophilic leukemia cells; the reactivity of B5 remained unchanged. A2 does not evidently interact with the same site on the Fc of IgE that is involved in binding to the rat basophilic leukemia cell Fc receptor; A2 exerted little influence on the binding of IgE to rat basophilic leukemia cells. Thus, the data indicate that the antigenic site for B5 is in the Fab region of the IgE molecule and that A2 reacts with the IgE Fc. Use of these antibodies to measure cell-bound IgE was also evaluated in dual label experiments, and potential problems in using divalent antibodies to quantitate cell surface antigens are discussed.

Animals↗
PubMed1983

Dissociation of autologous and allogeneic mixed lymphocyte reactivity by using a monoclonal antibody specific for human T helper cells.

A monoclonal antibody defining a population of human T helper cells was developed and shown to specifically block the autologous mixed lymphocyte reaction (AMLR). This antibody, termed KT69-7 (IgG1), recognized 62% of peripheral blood E rosette-positive (E+) cells while demonstrating negligible reactivity with E- cells, monocytes, granulocytes, EBV-transformed B cell lines, and mouse splenocytes. Separation of E+ cells into KT69-7+ and KT69-7- populations revealed that KT69-7+ T cells provided helper function in PWM-driven B cell differentiation, whereas KT69-7- T cells provided no help and may suppress this response. Modulation of membrane moieties by using KT69-7 or OKT4 plus goat anti-mouse IgG removed reactivity to both these antibodies, suggesting an association between these molecules recognized by these antibodies. In functional studies, KT69-7 selectively blocked the AMLR while demonstrating minimal or no effect on the allogeneic MLR (allo-MLR). Blocking of the autoreactivity occurred when either autologous B lymphocytes or macrophages were used as stimulators. The failure of KT69-7 to block the allo-MLR was not attributable to excessive allogeneic stimulus; KT69-7 failed to block even under conditions of limiting numbers of stimulator cells. KT69-7 thus appears to recognize a molecule on the surface of T helper cells required for recognition of autologous class II antigens.

Animals↗
PubMed1983

Characterization of non-human primate antisera to acute lymphoblastic leukemia (ALL): evidence for unique antigen(s) on childhood ALL of "T" phenotype.

A non-human primate antiserum was prepared to acute lymphoblastic leukemia of T-cell phenotype (T-ALL) and, after absorptions with normal blood elements, reacted by immunofluorescence and microcytotoxicity to all the T-ALL tested. In addition, the antiserum reacted with cells from about 70% of the common ALL studied and immunoprecipitated the common ALL antigen of 100,000 daltons. However, when the anti-T-ALL serum was absorbed with with lymphoblasts from common ALL, it failed to react with common ALL lymphoblasts, yet reacted significantly with cells from patients with T-ALL phenotype and defined a 100,000-dalton membrane component not found on common ALL lymphoblasts. In addition, sequential immunoprecipitation of 125I-labeled T-ALL membranes by anti-common-ALL serum followed by anti-T-ALL serum detected the T-ALL membrane component of 100,000 daltons that was not found on common ALL. Thus, our results demonstrate the presence of of a unique human T-ALL antigen present on all T-ALL distinct from the common ALL antigen.

Absorption↗
PubMed1983

Human mononuclear phagocyte-associated antigens. III. Relationship of cell surface antigen phenotype between cultured monocytes and tissue macrophages.

In order to determine the correlation between the in vitro model of monocyte differentiation and its in vivo counterparts, cell surface phenotypes of monocytes in culture and mature tissue macrophages were analyzed using monoclonal antibodies, M1/70, TA-1 anti-HLA-DR, and a heteroantisera prepared to macrophage cell line U937. Following 7 days in culture the reactivity of monocytes with M1/70 diminished from 70 +/- 9% to 31 +/- 8%. Similarly, the reactivity to TA-1 dropped from 88 +/- 8% to 23 +/- 7% and for anti-DR, from 79 +/- 5% to 41 +/- 16%. Reactivity with anti-U937 remained unchanged. This altered phenotype of cultured monocytes was found to approximate that of resident splenic macrophages (MO). In addition, freshly isolated monocytes and peritoneal exudate MO (PEMO) were found to be functionally similar in their inability to phagocytize via the C receptors. These results suggest that PEMO arriving recently into the peritoneal cavity from peripheral blood may be midway in transition between monocytes and mature MO, and that the phenotype and functional changes attributed to monocytes in culture may reflect changes that occur in vivo in the transition to tissue MO.

Antigens, Surface↗
PubMed1982

Clinical and immunological correlates of leukemia cutis in childhood.

Clinical features of three children with acute lymphoblastic leukemia complicated by leukemia cutis are described. All three patients appeared to have null cell disease, in contrast to adult cutaneous lymphoproliferative diseases which are generally T-cell disorders. Morphologically normal bone marrow specimens from one of these patients plus an additional four patients with isolated extramedullary relapses were also studied and found to be reactive to antisera defining leukemia associated antigens and/or human Ia-like antigens during six of eight relapse episodes. Such data may imply the need for systemic as well as local therapy when "isolated" extramedullary relapse occurs.

Antigens, Neoplasm↗
PubMed1982

Immunologic evaluation of long-term effects of childhood ALL chemotherapy: analysis of in vitro NK- and K-cell activities of peripheral blood lymphocytes.

Twenty-five children with acute lymphoblastic leukemia (ALL) were tested for natural killer (NK) and K-cell activity in vitro using the nonsensitized myeloid/erythroid cell line K562 and the K562 sensitized with rabbit antithymocyte globulin, respectively. The patients consisted of two groups: 1) 13 patients in continuous first remission undergoing maintenance chemotherapy and 2) 12 patients in remission for at least five years in whom chemotherapy had been discontinued at least six months before this study. The first group consistently demonstrated a marked depression in their NK activity and antibody-dependent cell-mediated cytotoxicity (K-cell activity), as compared with normal controls. In contrast, normal levels of cytotoxicity were found in the second group of patients off of all chemotherapy. One patient studied while on chemotherapy and on two occasions following discontinuation of maintenance medications demonstrated that while NK and K-cell activity was depressed during therapy, normal activity returned within days when immunosuppressive therapy was stopped. Thus, present modes of chemotherapy clearly had a profound effect on the in vitro NK and K-cell activity; however, no long-term effect on these functions was noted in our studies.

Adolescent↗
PubMed1982

Characterization of compounds shed from the surface of human leukemic myeloblasts in vitro.

Human leukemic myeloblasts shed glycoproteins from the cell surface during short-term in vitro culture. Shed surface glycoproteins yield a characteristic profile when studied by gel chromatography, isoelectric focusing, immune precipitation, and polyacrylamide gel electrophoresis. Isolation of immunologically active material yields a compound to approximately 75,000--80,000 daltons, with an isoelectric point of 7.6 to 7.9. Various morphological subtypes of acute myelogenous leukemia shed these compounds, but they are most easily obtained from the more differentiated M2 and M4 types as compared to the undifferentiated M1 type. The shed compounds appear to be quantitatively and qualitatively different from compounds shed by other leukemic cells or nonleukemic cells.

Cells, Cultured↗
PubMed1981

Genetic studies of an acardiac monster: evidence of polar body twinning in man.

Two maternally derived chromosome sets and both maternal histocompatibility antigen haplotypes were identified in the tissues of a malformed triploid acardiac twin that developed within the same chorion as its normal twin. These findings indicate that the twins arose as a result of independent fertilizations, by two different spermatozoa, of a normal haploid ovum and its diploid first-meiotic-division polar body.

Abnormalities, Severe Teratoid↗
PubMed1981

Acute myeloblastic leukemia-associated antigens: detection and clinical importance.

Antigenic compounds from the surface of leukemic myeloblasts are shed in vitro on short-term culture. Blast cells radiolabeled by lactoperoxidase iodination release soluble compounds that react immunologically with alloantisera to leukemia-associated antigens. Partially characterized soluble antigens were used to raise heteroantisera in monkeys that are selectively reactive with leukemic myeloblasts and unreactive with nonleukemic cells. Monkey heteroantisera were used to further characterize soluble leukemia antigens. Sera from patients with acute myeloblastic leukemia inhibit the reactivity of the heteroantisera, suggesting that soluble leukemic antigen is released in vivo as well.

Antibodies, Neoplasm↗
PubMed1981

Serological characterization of antibodies eluted from chronically rejected human renal allografts.

Serum samples collected pre- and post-transplant nephrectomy were screened for alloreactive lymphocytotoxins. Three patients demonstrated circulating anti-B cell antibodies with markedly increased cytotoxicity titers after nephrectomy, suggesting that there was active binding of antibodies within the renal allograft. Two of the postnephrectomy serum samples after absorption with platelets and B cells reacted by immunofluorescence with cultured primary kidney cells but not against B or T cells from the same donor. To clarify further the role of such alloreactive antibodies, eluates were prepared from 14 rejected renal allografts and were analyzed for reactivity to cultured primary kidney cells against different leukocyte targets and endothelial cells. Reactivity toward B cells and kidney cells was demonstrated with 80% of the eluates. Absorption experiments of the positive eluates demonstrated multiple types of alloreactive antibodies. In addition to anti-DR activity, eluates had antibodies reactive to kidney cell antigens, monocytes, macrophages, endothelial cells, and polymorphonuclear leukocytes. The demonstration of multispecific alloantibodies in eluates of rejected kidneys is consistent with an important role(s) in maintenance and/or rejection of the kidney allograft.

Antibody Specificity↗