Immuno-suppressive Effect of Human Alphafetoprotein: A Cross Species Study

Alphafetoprotein (AFP) is the major serum protein of fetal life in human and other mammalian species. The phylogenetical concervatism of AFP demonstrated by extensive Immunological cross reaction between human AFP and AFP of a number of species, suggest that AFP plays a general role in the successful pregnancy of all mammalian species. The present work clearly demonstrates the antiproliferative effect of human AFP on lymphocytes, harvested from normal human donors. The Inhibitory effect of human AFP is quite significant in the same dose during blastic transformations of the lymphocytes. In this study, peripheral blood mononuclear cells were Induced to blastic transformations with phytohaemagglutinin (PHA-M) and the effect of AFP was quantified by the Incorporation of [³H]-thymidine into newly synthesized DNA during 24 hrs pulse. Moreover, human AFP shows similar immuno-suppressive effect to other species of lymphocytes also. In all the three species (mouse, rat and hamster) studied, a parallelsm was noted In their respective percentage of thymidine incorporation values at the comparable doses. These results establish a cross species inhibitory effect of human AFP and it may be stated that this effect is directly targeted on T-helper cells and has no Interaction with interleuk in-2 (IL-2).     

Expression of alpha-fetoprotein receptors by human T-lymphocytes during blastic transformation

Alpha-fetoprotein (AFP) and transferrin (Tf) are actively internalized by many growing cells during ontogenic and neoplastic development, including human malignant T- and B-lymphoblastoid cells. Their internalization is, on the contrary, greatly diminished or absent in mature, non-proliferating elements. In the present work, peripheral blood mononuclear cells (PBMCs) and T-lymphocytes, harvested from normal human donors, were induced to blastic transformation with phytohemagglutinin (PHA) and their ability to uptake AFP and Tf was measured and compared with Tf uptake in the same conditions. The capacity of the cells to internalize both proteins was quantified by fluorescence activated cell sorter (FACS) using fluoresceinated derivatives of these proteins. The results obtained show a significant uptake of AFP by T-lymphocytes upon PHA stimulation. The values of AFP incorporation were similar for all the cells studied (PBMCs, T-cells and T4, T8 cell subsets). The time course of AFP uptake paralleled, under the same conditions, the uptake of Tf and the expression of IL2 receptors. AFP uptake increased rapidly from the zero time (resting T-cells) and reached a maximum around 72 hr after PHA activation. Scatchard analysis of kinetic data at 4 degrees C revealed for Hu-AFP one single group of specific binding sites in PHA activated T-lymphocytes with a dissociation constant of 3.03 x 10(-7) M and around 88,000 sites/cell. There results strongly suggest the transitory expression of AFP receptors in T-lymphocytes during blastic transformation.     

Inhibition of blastic transformation and immunoglobulin release in lymphocytes cultured in the presence of alpha-fetoprotein (AFP).

Blastic transformation of phytohemagglutinin-stimulated lymphocytes in cultures containing various concentrations of homogenous alpha-fetoprotein (AFP) was studied. It was found that AFP in concentrations of 4-12 microgram/ml inhibits both blastic transformation and immunoglobulin release (IgA, IgG) in lymphocyte cultures. It is suggested that AFP plays an important role in immunoregulation during the fetal life.     

Immunochemical Properties of Alpha-Fetoprotein (AFP) and Antibodies to Autologous AFP

Alpha-fetoprotein (AFP) is a strong immunogen when injected into another species, but does not elicit an immune response in the species of origin of the AFP. AFPs from different mammalian species are crossreactive. AFP and albumin show sequence homology. They do not crossreact in their native state, but their unfolded (reduced and carboxamidomethylated) forms are immunologically cross reactive.

Antibodies to autologous AFP can be induced in animals by immunization with heterologous or modified homologous AFP. These antibodies eliminate the AFP normally measurable in the serum and deay the elevation of serum AFP caused by hepatomas, but do not protect against such tumors.     

Immunochemical Properties of Alpha-Fetoprotein (AFP) and Antibodies to Autologous AFP

Alpha-fetoprotein (AFP) is a strong immunogen when injected into another species, but does not elicit an immune response in the species of origin of the AFP. AFPs from different mammalian species are crossreactive. AFP and albumin show sequence homology. They do not crossreact in their native state, but their unfolded (reduced and carboxamidomethylated) forms are immunologically cross reactive.

Antibodies to autologous AFP can be induced in animals by immunization with heterologous or modified homologous AFP. These antibodies eliminate the AFP normally measurable in the serum and deay the elevation of serum AFP caused by hepatomas, but do not protect against such tumors.     

AN EXPERIMENTAL STUDY ON THE SIGNIFICANCE OF THE BONE MARROW LYMPHOCYTE IN HAEMATOPOIETIC REGENERATION FOLLOWING ACUTE INJURY DUE TO 60CO IRRADIATION and CYTOTOXIC DRUGS*

Haematopoietic cells of the rat bone marrow were killed almost completely by using hydroxyurea (OHU), cytoslne arabinoslde (ara-C), ⁶⁰Co irradiation and busulfan. The relation between the regeneration of haematopoietic cells of the bone marrow and the behavior of the bone marrow lymphocytes and related cells was investigated quantitatively. Bone marrow lymphocytes and related cells were cytologlcally classified Into lymphocytes, transitional cells and blastic cells on the smeared preparation. Comparing the results of the experiment using OHU 2.5 g/kg with those using whole body irradiation of ⁶⁰Co 700R, the absolute number of nucleated cells In the bone marrow was reduced more prominently in the former case than in the latter. Nevertheless, regeneration of haematopoietic cells began earlier In the former case than in the latter. In the experiment using OHU 2.5 g/kg, haematopoietic cells in the bone marrow almost completely disappeared promptly after the treatment. On the contrary, the bone marrow lymphocytes were rather well preserved, making up 59% of control on the 1st day and 54% on the 2nd day. Moreover, it was evident that the decrease in number of bone marrow lymphocytes and the increase in number of transitional and blastic cells occurred simultaneously around the 4th day after the last dosage, just prior to the haematopoietic regeneration. On the 8th day after whole body irradiation with ⁶⁰Co 700R, in parallel with the appearance of haematopoietic regeneration, the bone marrow lymphocytes, transitional cells and blastic cells were the predominant populations In the regenerating bone marrow. In the experiment using ara-G 600 mg/kg, the number of transitional cells increased evidently prior to haematopoietic regeneration. The author concluded that regeneration of bone marrow haemato-poiesis can take place earlier and more rapidly, when the bone marrow lymphocytes are provided In sufficient numbers.     

Localization and Some Biological Properties of Pig Alpha-fetoprotein

In studies of the cellular localization of AFP with the use of immunofluorescent, immunochemical and immunoautoradiographic techniques we concentrated in the course of prenatal ontogeny of pigs on the mesenchymal haemopoictic population of lymphatic and haemopoietic organs of these animal species. A marked AFP positivity was demonstrated already in haemopoietic cells of yolk sac, but also in other organs of embryonic and fetal haemopoiesis. In the course of intrauterine development the percentage of AFP-positive haemopoietic cells decreases and postnatally the AFP positivity of haemopoietic cells does not occur. The decrease in AFP-positivity of haemopoietic fetal cells is in correlation with the subsequent decrease in the intensity of extramedullary haemopoiesis. In the system in vitro the inhibitory effect of pig AFP on T and B cell mitogen-induced blast transformation of lymphocytes was demonstrated, similarly as on the mixed lymphocyte reaction. That effect of AFP is dependent on its presence in the first 24 hrs of stimulation and is not species specific. In fetal cell suspensions of lymphatic and haemopoietic organs of pigs their capacity for blastogenic transformation with anti-AFP serum was demonstrated.     

Effects of HIV-1 peptides on T-cell receptor variable beta chain families

Superantigens (SAGs) selectively stimulate expansion and then deletion of specific T cell antigen receptor (TCR) variable beta chain (Vbeta) families. We investigated six synthetically produced HIV-1-related peptides for evidence of SAG activity: three derived all or in part from the transmembrane gp41 protein and three from the genetic sequence of the tRNA binding region. The first three were chosen because they are highly immunogenic; the second three, because their genetic sequence is completely homologous to a region of the mouse mammary tumor virus, a known superantigen. We cultured peripheral blood mononuclear cells (PBMC) of HIV-negative, healthy human donors with each of these six HIV-1 peptides. Resting and blastic CD4(+) and CD8(+) lymphocytes were assessed pre- and post-culture using 3-color cytofluorometry and monoclonal antibodies to CD4, CD8, and 14 human TCR Vbeta families. Significance testing was done using a Student t-test. Two of the HIV-1 peptides showed possible SAG activity, one from gp41 transmembrane protein, and one from tRNA binding region. Peptide JJ1, from gp41, was associated with an increased percentage of resting and blastic Vbeta 5, 8, and 21 in CD4(+), but not CD8(+) lymphocytes (3/3 donors, p = 0.014, p = 0.011, and p = 0.019, respectively, for blastic CD4(+) lymphocytes). Peptide JJ5, from the tRNA binding region, was associated with an increased percentage of resting and blastic Vbeta 5, 12, 16, and 17 in CD8(+) but not CD4(+) lymphocytes (4/4 donors for blastic CD8(+) lymphocytes, 3/4 for resting CD8(+) lymphocytes, p < 0.05 for each Vbeta family, for blastic CD8(+) lymphocytes). These results suggest that peptide JJ1 may have SAG activity restricted to CD4(+) lymphocytes and that peptide JJ5 may have restricted cytotoxic activity, associated with CD8(+) cell responsiveness. For both, the activities would lead to increased localized cytokine production and work to the advantage of the virus. These antigens might thus represent potential targets for future antiretroviral therapy.     

Central nervous system involvement in a patient with chronic lymphocytic leukemia and non-Hodgkin's lymphoma (Richter's syndrome), with concordant cell surface immunoglobulin isotypic and immunophenotypic markers

Central nervous system (CNS) involvement in Richter's syndrome has not been previously described. This report describes a 45-year-old man with the simultaneous occurrence of B-cell chronic lymphocytic leukemia (CLL), extramedullary large cell non-Hodgkin's lymphoma (NHL), and malignant lymphoid meningeal involvement. In this case, peripheral blood lymphocytes, cerebrospinal fluid (CSF) lymphoblasts, and malignant cells in surgical biopsy tissue obtained from a soft tissue mass all stained concordantly for immunoglobulin isotypes and for B-cell immunophenotypic markers, supporting the hypothesis of a clonal origin for the three malignant cell populations. These observations suggest that the different tumors in Richter's syndrome (CLL and NHL) may represent the clonal progression of a common neoplasm rather than independent neoplastic events. Richter's syndrome and other transformations of lymphoid malignancies (prolymphocytic transformation of CLL, blast crisis of CLL, and blastic transformation of NHL) may all represent possible routes of progression in the natural history of a single neoplasm. The present case also suggests that, in patients with B-cell CLL with CNS symptoms, the possibility of blastic transformation presenting as CNS lymphoma deserves consideration.     

Phenothiazine-induced alterations of immune response in experimental tick-borne encephalitis: morphological model analysis of events.

The depressive effect of trifluoperazine (TFP), a phenothiazine derivative, on the morphology of the development of immune response (IR) (humoral and cell-mediated component) was studied in mice given tick-borne encephalitis (TBE) virus, sheep red blood cells (SRBC) or the BCG vaccine. This effect was manifested by a decrease in the mitotic activity of lymphocytes and in the number of blastic transformations after antigenic stimulation. In virus-infected and TFP-given mice, lowered levels of specific virus neutralizing antibody (VNA), together with a pronounced reduction of the inflammatory response in the brain were found. No signs of cytotoxicity following administration of the drug were observed. The mechanism of the immunodepressive action of TFP are discussed.     

Immunosuppressive Characteristics of Human AFP: Effect on Tests of Cell Mediated Immunity and Induction of Humam Suppressor Cells

Murine AFP has been reported to be immunosuppressive in a variety of systems. However, the extent and degree of inhibition has varied in different species and laboratories. Therefore, we have examined the potential suppressive effect of purified human AFP on several in vitro tests of cellular immunity and the potential mechanism of its action AFP purified from fetal and liver cancer sera significantly inhibited mitogen and antigen-induced proliferative responses but had no effect on lymphocyte E rosetting, MIF production or mitogen induced T cell cyto-toxicity to Chang target cells. Purified human AFP induced human suppressor cell activity, capable of suppressing a one-way mixed lymphocyte reaction (MLC). In contrast to Con A induced suppressor cells, AFP induced suppressor cell activity was overcome by mitogen augmentation of the proliferative response in MLC. These data suggest that the inhibition of lymphocyte proliferation by human AFP may be mediated by the induction of a subpopulation of human suppressor cells. Furthermore, mitogen induced cell mediated cytotoxicity was partially inhibited by primary liver cancer serum and completely inhibited by newborn cord serum, in contrast to purified fetal or tumor AFP which had no effect. These data suggest that there are other immunosuppressive factors in fetal and tumor serum which require further characterization. These other serum factors may be responsible for some of the immunosuppressive effects attributed to AFP. Although AFP is unlikely to play a major immunosuppressive role physiologically in vivo, its selective effect on proliferative responses, apparently mediated by suppressor cells, may prove to be a useful pharmacologic probe of the mechanism of these in vitro lymphocyte responses and biological interactions.     

Immunosuppressive characteristics of human AFP: effect on tests of cell mediated immunity and induction of human suppressor cells.

Murine AFP has been reported to be immunosuppressive in a variety of systems. However, the extent and degree of inhibition has varied in different species and laboratories. Therefore, we have examined the potential suppressive effect of purified human AFP on several in vitro tests of cellular immunity and the potential mechanism of its action. AFP purified from fetal and liver cancer sera significantly inhibited mitogen and antigen-induced proliferative responses but had no effect on lymphocyte E rosetting, MIF production or mitogen induced T cell cytotoxicity to Chang target cells. Purified human AFP induced human suppressor cell activity, capable of suppressing a one-way mixed lymphocyte reaction (MLC). In contrast to Con A induced suppressor cells, AFP induced suppressor cell activity was overcome by mitogen augmentation of the proliferative response in MLC. These data suggest that the inhibition of lymphocyte proliferation by human AFP may be mediated by the induction of a subpopulation of human suppressor cells. Furthermore, mitogen induced cell mediated cytotoxicity was partially inhibited by primary liver cancer serum and completely inhibited by newborn cord serum, in contrast to purified fetal or tumor AFP which had no effect. These data suggest that there are other immunosuppressive factors in fetal and tumor serum which require further characterization. These other serum factors may be responsible for some of the immunosuppressive effects attributed to AFP. Although AFP is unlikely to play a major immunosuppressive role physiologically in vivo, its selective effect on proliferative responses, apparently mediated by suppressor cells, may prove to be a useful pharmacologic probe of the mechanism of these in vitro lymphocyte responses and biological interactions.     

Stimulatory Effect of Human Alpha-Fetoprotein and its Molecular Variants on in-Vitro-induced Lymphocyte Blastogenesis

Recent experiments suggested that alpha-protein (AFP) may have immunoregulatory properties and play a role in protecting the fetus from rejection by the mother. The present study was performed to determine whether purified human AFP, its molecular variants separated on Lens culinaris agglutinin, and fetal serum albumin showed immunoregulatory activiiy on in vitro transformation of normal human lymphocytes by mitogens or by allogeneic cells. Human AFP and fetal serum albumin were purified from human whole fetuses by immunoabsorption, followed by acid elution. AFP variants (HLI, HL2, HL3, HL4) were separated by lectin affinity chromatography. The proteins were tested in lymphocyte cultures stimulated by concanavalin A, phytohaemagglutinin and pokeweed mitogen and in mixed lymphocyte cultures. Four batches of AFP and one batch of fetal albumin, in the concentration range of 0-100 μg/ml and in one experiment up to 2 mg/ml, had a stimulatory effect on lymphocytes. One batch of human AFP showed inhibitory effect with low reproducibility. The variants had a stimulatory effect except for HL3, which was found to be slightly inhibitory in phytohaemagglutinin stimulated cultures when compared with cultures without AFP, but there was no significant difference when compared with cultures in which AFP was replaced by its dialysate. Thus, the results reported here are not consistent with the conclusion that human AFP has a significant immunosuppressive effect on man. Hypotheses about causes of discrepancies are analysed.     

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.     

Presence of the Philadelphia chromosome (Ph1) in pokeweed mitogen stimulated lymphocytes during chronic phase of chronic myelocytic leukemia (CML)

There has been a lack of direct cytogenetic studies on lymphocytes in the chronic phase of chronic myelocytic leukemia (CML). Peripheral blood mononuclear cells from seven patients in the chronic phase and on in the blastic phase of Ph1-positive CML were cultured in the presence of phytohemagglutinin (PHA) and pokeweed mitogen (PWM). Preparations adequate for analysis were obtained from eight PHA and five PWM stimulated cultures. Cytogenetic studies on the PWM stimulated cultured cells revealed, in one patient, the presence of the Philadelphia chromosome (Ph1) in 23/25 metaphases. The PHA stimulated lymphocytes from the same patient were all Ph1 negative. Lymphocytes from PHA and PWM stimulated cultures from the other six patients in the chronic phase and the one patient in blastic crisis were all Ph1 negative. The one positive result suggests that some B lymphocytes contain the Ph1 and that there is a common hematopoietic stem cell for B lymphocytes as well as the myeloid, erythroid, and megakaryocytic series.     

Productin of Basic Fetoprotein in Human Peripheral Lymphocytes during Blastic Transformation

To clarify the significance of basic fetoprotein (BFP) in lymphocytes, we investigated whether BFP is produced in lymphocytes during blastic transformation. Peripheral blood lymphocytes obtained from 14 adults were cultured under the stimulation of lectins. The concentration of BFP in the culture medium (extracellular BFP) was estimated serially. The incorporation of [6-³ H] thymidine was assayed simultaneously. The intracellular BFP was measured by dual flow cytometry for DNA and BFP. A lymph node was studies immunohistochemically. Serum BFP was measured in four cases of lumphocytic leukaemia. In two cases, dual staining was performed. The intracellular BFP of the mitogen-stimulated lymphocytes was increased within 24 h. The extracellular BFP was increased exponentially from 72 h. The extracellular BFP at 96 h did not correlate with the [³H]-thymidine incorporation. The intracellular BFP increase began in G₁ phase. Immunostaining showed that the B cells also produced BFP. The
serum BFP level in leukaemia was high in 1 of 4 cases and the leukaemic cells in two cases showed high intracellular BFP content. These observations indicate that BFP is produced in activated human lymphocytes and in lymphocytic leukaemic cells. The production of BFP during blastic transformation will be a useful new in vitro model for studying the biological role of BFP, and BFP labelling may offer some new possibilities for study of lymphocytes.     

Antigen-binding small lymphocytes in the guinea-pig: II. The immunological response to purified protein derivative of mammalian tuberculin

A mean of 6.9 per cent of small lymphocytes in peripheral blood preparations and between 1.8 and 2.4 per cent of small lymphocytes in lymph node, spleen, bone marrow and thymus preparations from unimmunized guinea-pigs bound ¹²⁵I-labelled purified protein derivative of mammalian tuberculin (mammalian PPD). The percentage of these cells fluctuated but did not alter substantially after immunization with BCG or with BCG emulsified with human thyroglobulin (HTg) in Freund's incomplete adjuvant (FIA). Blocking experiments indicated that the binding of ¹²⁵I-labelled mammalian PPD was specific and there was tentative evidence that the lymphocyte receptors may be IgG. A comparison is drawn between the observed time course of ¹²⁵I-labelled mammalian PPD-binding small lymphocytes and the response of lymphocytes sensitive to strong histocompatibility antigens, and it is proposed that the propensity of certain antigens to induce a delayed hypersensitivity-type response is related to the presence of substantial numbers of antigen-binding cells in unimmunized animals.

A noteworthy incidental finding was an unexplained depression in the cellular and humoral responses to mammalian PPD in guinea-pigs that had been immunized with HTg—BCG—FIA emulsion.

     

Characterization of murine newborn inhibitory T lymphocytes: functional and phenotypic comparison with an adult T cell subset activated in vitro by alphafetoprotein

Inhibitory T lymphocytes isolated from the spleens of newborn CBA/J mice which have high intrinsic levels of alpha-fetoprotein (AFP) were compared, in terms of surface antigen phenotype and mode of immunosuppressive action, with a population of adult spleen T cells activated in vitro by a 4-day preculture in the presence of purified AFP. The suppressing ability of these two groups of T cells was assayed on in vitro antibody synthesis of adult spleen cells to the T-dependent (TD) and T independent (TI) antigens, sheep red blood cells and 2,4-dinitrophenylated Ficoll. Negative selection of T cell subpopulations with antisera and complement showed that the inhibitory activity of newborn and adult AFP-activated T cells on anti-sheep red blood cell responses was abrogated by anti-Thy-1 anti-Lyt 1, and by anti-Ia^k (A. TH anti-A. TL), whereas anti-Lyt 2 antiserum and complement had no effect. Cytotoxic pretreatment with a panel of alloantisera specific for distinct products of major histocompatibility complex I subregions indicated that the Ia antigens expressed on the inhibitory T cells included I-J, but not I-EC determinants. Newborn and adult AFP-activated inhibitory T cells could thus be shown to belong to a very similar, if not identical, subset of T lymphocytes characterized by the Thy-1⁺, Lyt-1⁺2^?, I-J⁺ phenotype. Both groups of T lymphocytes were shown to behave like efficient suppressor inducer cells in that they augmented TD antibody responses when added to purified B cell cultures which could not respond to TD antigen on their own, but caused strong inhibition of these responses when normal T cells were present. Dilution analyses of the two groups of inhibitory T cells showed that efficient suppressive activity was highly selective for TD responses, compared with a relatively weak inhibitory effect on TI responses. Passive administration of anti-I-J alloantibodies into newborn animals resulted in a significantly increased ability to respond to TD antigen, suggesting an anti-I-J-mediated disruptive effect on newborn suppressor mechanisms. Our findings, therefore, indicate that TD antibody responses in newborn mice are regulated by an I-J⁺ T cell-mediated feedback inhibition circuit. Based on functional and phenotypic analyses, our results further suggest the probable identity of the naturally occurring inhibitory T cells in newborn mice and a subset of adult spleen T cells activated in vitro by AFP. This supports the contention that AFP may function as an important immunoregulatory agent in vivo.     

In vitro induction of sister chromatid exchanges and chromosomal aberrations in peripheral lymphocytes of the oyster toadfish and american eel

A series of experiments was conducted to characterize the proliferation of oyster toadfish lymphocytes in medium containing 5-bromodeoxyuridine (BrdUrd) and to determine the effectiveness of cytogenetic endpoints for assessing the genotoxic effects of in vitro exposure of toadfish and eel lymphocytes to known mammalian clastogens. Although the rate of proliferation of toadfish lymphocytes was low compared to that of mammalian lymphocytes, the effects of increasing BrdUrd concentrations were similar, in that proliferation exhibited a concentration-dependent inhibition for concentrations above 10 μM BrdUrd, and sister chromatid exchange (SCE) frequencies exhibited a concentration-dependent increase for concentrations above 100 μM BrdUrd. Mitomycin C (MMC) and ethylene dibromide (EDB) induced concentration-dependent increases in chromatid-type exchange and SCE frequencies with least effective concentrations (control SCE frequency divided by the slope of the least-squares line) for SCE induction by MMC (6.8 × 10^?9 M) and EDB (2.6 × 10^?4 M) that were comparable to or slightly lower than those that have been obtained with mammalian in vitro systems. In vitro exposure of toadfish lymphocytes to dimethoate (DIM) induced a concentration-dependent increase in SCE frequency with a least effective concentration of 2.8 × 10^?3 M that was much higher than that observed with mammalian in vitro systems. In vitro exposure of American eel lymphocytes to MMC also induced a concentration-dependent increase in the frequency of chromosomal aberrations and SCEs with a least effective concentration for SCE induction of 2.0 × 10^?9 M. These results indicate that cytogenetic endpoints can be effectively scored with cultured lymphocytes from these and perhaps other fish species with comparable karyotypes that contain an average of at least 0.07 pg DNA/chromosome.     

Demonstration of immunoglobulin-related molecules on human peripheral blood T lymphocytes using chicken anti-F(ab'')2 and anti-IgM antibodies.

A mean of 98% of lymphocytes in T-enriched preparations of human peripheral blood bound purified chicken anti-human F(ab')2 antibodies to their surface membranes as demonstrated by the mixed antiglobulin rosetting reaction (MARR). By reverse passive hemagglutination these antibodies reacted strongly with kappa light chains and with Fd gamma but gel diffusion analyses, absorption on affinity columns and inhibition experiments established that the anti-F(ab')2 antibodies were not isotype specific and that there was extensive serological cross-reactivity between Fd gamma and kappa and probably also between Fd gamma and mu chains. The antigenic determinants recognized on the T-cells surfaces were not shared by Ig fractions from several other mammalian species. Trypsin treatment of lymphocytes removed all determinants recognized by anti-F(ab')2 antibodies from approximately two-thirds of the cells but these cells almost completely re-expressed these determinants during in vitro culture; this indicates that the T-cell determinants seen by anti-F(ab')2 antibodies are T cell products and do not represent adsorbed Ig. Complete inhibition of the MARR by human F(ab')2 excludes false positive rosette formation due to contaminating specificities directed against non-Ig molecules on T cells. Together the various findings are consistent with the conclusion that most human peripheral blood T cells express Ig or Ig-related molecules in their surface membranes. A mean of 13% of lymphocytes in T-enriched preparations were reactive with mu-chain specific chicken antibodies; it may be that a minority of T cells express mu chain determinants in addition to those recognized by anti-F(ab')2 antibodies.