Growth of normal human T lymphocytes induced by monoclonal antibody to the T cell antigen receptor

A monoclonal antibody (mAb) called 30-3D6 has been raised against the T cell antigen receptor analogue on a human T cell leukemia cell line HPB-ALL. This mAb comodulates the T3 molecule on HPB-ALL and precipitates the heterodimeric structure previously described as a T cell idiotypic receptor analogue on this cell line. 30-3D6 reacts with a variable percentage of normal T cells (up to 6%) depending on the donor and this number is stable on repeated sampling and is not affected by the temperature of the reaction. When normal T cells from a high frequency donor are stimulated with 30-3D6 and interleukin 2 in vitro the idiotype-positive (Id+) population can be expanded. Large numbers of greater than 90% Id+ T cells can be generated. Id cells are present in both the helper and cytotoxic suppressor subsets.     

Production and characterization of monoclonal antibodies to guinea pig lymphoid differentiation antigens

We have prepared 2 mouse monoclonal antibodies which react with differentiation antigens on guinea pig lymphoid cells. Monoclone 5AB2 recognizes an antigen expressed on both T and B lymphocytes and absent on macrophages. It has proven useful in the preparation of populations of antigen presenting cells which are free of T and B lymphocytes. The second monoclonal, 8BE6, is specific for peripheral T cells and 10% of thymocytes. It reacts with a 68,000 dalton molecule which is also expressed on the guinea pig B cell leukemia, EN-L2C. 8BE6 has proven to be lytic for peripheral T cells in the presence of rabbit complement and has been used to deplete T cells from heterogenous cell populations.     

Inhibition by anti-HLA class II monoclonal antibodies of monocyte-dependent T cell proliferation induced by monoclonal antibody OKT3

The inhibitory effect of monoclonal antibodies (mAb) to monomorphic (locus-restricted and locus-shared) and polymorphic determinants of HLA class II antigens on the monocyte-dependent proliferation of T cells stimulated with mAb OKT3 has been studied. The effect appears to be specific, dose dependent, is not mediated by the Fc portion of mAb and reflects their interaction with the corresponding determinants. The anti-HLA class II mAb do not have to be present in the culture throughout the incubation period, but are essential in early phases of mAb OKT3 T cell activation. Both monocytes and T cells are the targets of the inhibition exerted by the anti-HLA class II mAb. Their inhibitory effect involves several steps in the sequence of events which leads to T cell proliferation, including interleukin (IL) 1 and 2 secretion, and IL2 receptor expression.     

Homotypic aggregation of murine T lymphocytes induced by anti-Thy-1 monoclonal antibodies.

During the course of studies of anti-Thy-1-mediated T-cell activation, we found that anti-Thy-1 monoclonal antibodies (mAb) could induce strong homotypic aggregation of murine T-lineage cells. We demonstrated that anti-Thy-1 mAb-mediated T-cell aggregation started at 10 min and reached maximum level 1 hr after addition of antibody. It was temperature dependent, requiring metabolic energy and cytoskeletal integrity similar to that mediated by phorbol myristate acetate (PMA). But the striking difference between anti-Thy-1 mAb-mediated cell aggregation and PMA-mediated cell aggregation was that the latter but not the former was blocked by anti-LFA-1 mAb. This indicates that, unlike treatment with PMA, anti-CD2 mAb or anti-CD3 mAb, anti-Thy-1 mAb treatment of T lymphocytes does not induce LFA-1 activation for cell adhesion. Murine neuroblastoma cells were not induced to aggregate by anti-Thy-1 mAb treatment, although murine T lymphoma cells were aggregated by anti-Thy-1 mAb. The T-lineage cell specificity of anti-Thy-1-mediated aggregation was further shown by the Thy-1 gene transfection into non-Thy-1 expressing cell lines. Thy-1.1 gene transfected mastocytoma cells were not aggregated by anti-Thy-1.1 antibody.     

Differentiation antigen on murine B lymphocytes defined by monoclonal antibodies

Spleen cells from an AKR/J X DBA/2J F1 mouse immunized with NZB/BIN spleen cells were fused with SP2/0-Ag14. Two hybrid cell lines, B220-1 and B220-2, were established that secreted antibody to the B-lineage specific B220 antigen. B220-1 and B220-2 are present on 45-55% of splenic and bone marrow lymphocytes and absent from thymus. By flow cytometry, all immunoglobulin-bearing cells were stained by these monoclonal antibodies. Although these monoclonals do not stain thymocytes, they do react weakly with Lyt-2+ peripheral T cells. Dual parameter analysis of B lymphocytes using RA3-3A1 or 14.8 show that these monoclonals recognized the same population. Prior incubation with RA3-3A1 or 14.8 was unable to completely block the binding of B220-1 or B220-2, implying that the epitopes recognized are different from the previously described monoclonal antibodies. Immunoprecipitation of the splenic lymphocyte reveals a molecule which migrates on SDS-PAGE as a single band with MW of 220,000 daltons. Expression of the distinct antigens recognized by B220-1 and B220-2 varied among mouse strains, indicating previously unappreciated polymorphism of the B220 molecule. These monoclonals are useful for cytotoxic elimination of B cells and for three-color flow cytometry.     

T cell proliferation induced by anti-CD3 antibodies: requirement for a T-T cell interaction

In the presence of interleukin 2 (IL2), soluble anti-CD3 monoclonal antibodies can stimulate highly purified normal T lymphocytes to proliferate. In these experiments HLADR+ T cells constituted 13 to 20% of the total cell population, and other HLADR+ cells, such as monocytes and B lymphocytes, constituted less than 1% of the population. When the HLADR+ T cells were removed from the total T cell population by cytofluorometric sorting, the residual HLADR- T cells failed to respond to soluble anti-CD3 plus IL2. When the separated HLADR+ T cells were recombined with the HLADR- T cells, a response was again found. This response was dependent on the dose of HLADR+ T cells added in the mixture. Irradiation individually of the HLADR+ and DR- T cells revealed that the proliferation in the cell mixture was predominantly, if not exclusively, by the HLADR- T cells. The ability of the HLADR+ T cells to provide a signal necessary to this proliferation was radioresistant. These data indicate that under the conditions of these experiments HLADR+ ("activated") T cells provide a signal necessary to the responsiveness of previously resting T cells.     

Production and use of rat monoclonal antibodies to the human myeloid cell nuclear differentiation antigen

A dot immunoblot screening assay was used to identify rat monoclonal antibodies to a human myeloid cell differentiation-specific nuclear antigen (MNDA). The selection was based on the positive reaction of hybridoma cell supernatants with a concentrated nuclear protein extract prepared from late stage human myeloid leukemia cells that express MNDA (HL-60) coincident with a negative reaction with the same extract prepared from a non-expressing more immature human myeloid leukemia cell line. The approach provided an efficient method for obtaining monoclonal antibodies to a specific low abundance nuclear antigen that has not been purified. Sixteen wells from three fusions contained antibody displaying a specific reaction with the nuclear protein fraction obtained from the HL-60 cells. Immunoblotting analysis revealed that all of the sixteen specific hybridoma cell lines produced antibody against the same Mr 55,000 nuclear antigen. Selecting hybridoma cells that produce antibody reactive with the native antigen provided antibody suitable for detecting MNDA in immunocytochemical tests. The rat monoclonal antibodies were purified and coupled to CNBr-activated agarose and carbonyldiimidazole-activated agarose. Although both antibody affinity matrices exhibited the same antigen binding capacities, the matrix prepared using carbonyldiimidazole-activated agarose bound the MNDA with a high level of specificity while the matrix prepared from CNBr-activated agarose bound numerous other nuclear proteins.     

Inhibition of T cell proliferation by antibodies to synthetic peptides

While T cell proliferation to antigen in the presence of antigen-presenting cells is well known to be readily inhibited by antibodies directed against Class II major histocompatibility complex (MHC) (Ia/HLA-DR) products, it has not been possible to inhibit proliferation by antibodies directed against the antigen. Because of the implications of these observations for targets of T cell recognition, this phenomenon was reinvestigated using human T cell clones, recognizing a small (24 amino acid) synthetic peptide (termed p20) derived from the influenza hemagglutinin-1 molecule. It was found that proliferation of clones to p20 was inhibited efficiently (less than 90%), using p20 as antigen, and rabbit anti-p20. Inhibition was possible either by coculturing p20 antigen and antibody to p20 with cloned T cells and antigen-presenting (E-) cells, or by pulsing antigen-presenting cells with antigen prior to a brief incubation with antibody before washing the E- cells and using them to stimulate cloned T cells. These results do not indicate why previous attempts had failed, but in view of the different techniques available now (cloned T cells, small synthetic polypeptides, and antibody raised against polypeptide) we investigated the influence of these parameters. It was found that, using cloned T cells, the form of the antigen was of importance, as antibody inhibition of the response to hemagglutinin or whole influenza A was much less apparent. These differences were interpreted as being due to greater access of anti-p20 to p20 than to hemagglutinin or influenza. If uncloned T cell lines were used, inhibition was also much harder to detect. This was interpreted as masking of inhibition of the response of some clones in the line by interleukin 2-induced recruitment.     

Antigen-specific cytotoxic T cell and antigen-specific proliferating T cell clones can be induced to cytolytic activity by monoclonal antibodies against T3

T3 is a human differentiation antigen expressed exclusively on mature T cells. In this study it is shown that anti-T3 monoclonal antibodies, in addition to their capacity to induce T cells to proliferate, are able to induce antigen-specific cytotoxic T lymphocyte clones to mediate antigen nonspecific cytotoxic activity. It is furthermore shown that anti-T3 reagents are able to trigger lytic activity in T cell clones characterized as noncytotoxic antigen-specific proliferating T cells. The data presented indicate that perturbation of T3 can trigger the lytic machinery in cytolytic as well as noncytolytic T cell clones.     

Regulation of T cell proliferation by anti-CD49d and anti-CD29 monoclonal antibodies.

The beta 1 integrin VLA-4 (alpha 4 beta 1, CD49d/CD29), which is expressed on a large subpopulation of peripheral blood T lymphocytes, functions as a receptor for the endothelial adhesion protein VCAM-1 and the extracellular matrix protein fibronectin. Previous studies showed that immobilized fibronectin enhanced anti-CD3 monoclonal antibody (mAb)-induced T cell proliferation through binding to the integrins VLA-4 and VLA-5 (alpha 5 beta 1, CD49e/CD29). We studied the ability of the anti-CD49d mAb L25 to potentiate proliferation. T cell proliferation was induced by subthreshold concentrations of anti-CD3 mAb (mAb OKT3) coimmobilized with mAb L25 but not with coimmobilized anti-CD29 (beta 1) mAb. Soluble anti-CD29 mAb inhibited the proliferation induced by coimmobilized mAb OKT3 and L25 but not proliferation induced by mAb OKT3 with PMA or coimmobilized anti-CD26 mAb.     

Studies on the differentiation of T lymphocytes in sheep. I. Recognition of a sheep T-lymphocyte differentiation antigen by a monoclonal antibody T-80

The results presented in this paper demonstrate that a mouse IgM monoclonal antibody (T-80) recognizes an antigen on cells of the T-lymphocyte lineage of sheep. However, this antibody does not identify all T cells, as 10-20% of thymocytes and some peripheral-blood T cells are negative. T-80- thymocytes reside in the medulla. The majority of cortical thymocytes are T-80+ and classified as dull cells on the basis of antigen density per cell as measured by flow microfluorometry. In contrast, T-80+ cells in the periphery can be categorized into two populations, i.e., dull cells and bright cells. Suggestive evidence was obtained that bright T-80+ cells are fast recirculating T cells, whereas dull cells are sessile or less easily mobilizable T cells in the periphery. In foetal environment, over 90% of thymocytes and approximately 5% of spleen cells are T-80+ at 54 days of gestation (gestation period = 150 days), which may indicate that T-cell emigration from the thymus commences well before mid-gestation in sheep.     

Antigen-presenting capacity of guinea pig B lymphocytes in T cell proliferative response in vitro

The capacity of normal (unprimed) B cells and keyhole-limpet-hemocyanin(KLH)-primed B cells to present the antigen KLH to KLH-primed T cells in the guinea pig was examined with in vitro assay of lymphocyte proliferative response. Antigen-pulsed B-lymphocyte population, extensively devoid of macrophages (M phi), induced the proliferative response of KLH-primed T lymphocytes, although less effectively than the peritoneal M phi. The antigen presentation was antigen-specific. There was no substantial difference between the magnitude of T-cell response induced by KLH-primed B-cell population and that stimulated by unprimed, normal B-cell population. The antigen-presenting capacity of the B-cell population was abrogated by pretreatment with anti-guinea pig immunoglobulin (Ig) or anti-I-region-associated (Ia) antigen antiserum and complement, whereas it was not affected with anti-guinea pig M phi antiserum and complement. From studies using strain 2 and strain 13 guinea pigs, histocompatibility requirement between antigen-pulsed B cells and antigen-reactive T cells was suggested: B lymphocytes, as well as M phi, did elicit proliferative response to specific antigen, KLH or purified protein derivative of tuberculin (PPD), in syngeneic, but not in allogeneic, T cells. These results suggest that the Ia-positive, surface-Ig-bearing guinea-pig B lymphocytes - not only KLH-primed B cells but also unprimed B cells - are capable of presenting antigen to primed T cells in a major histocompatibility complex(MHC)-restricted fashion.     

Signals involved in T cell activation. T cell proliferation induced through the synergistic action of anti-CD28 and anti-CD2 monoclonal antibodies

Monoclonal antibodies (mAb) directed against the T cell differentiation antigen CD28 (Tp44) induce proliferation of resting T lymphocytes in the presence of phorbol esters. Moreover, it has been reported that such antibodies augment and sustain T cell proliferation induced by soluble antigens, phytohemagglutinin and anti-CD3 mAb. Recently, we have shown that in monocyte-depleted T cell suspensions, anti-CD28 mAb 9.3 and Kolt-2 were able to circumvent the requirement for interleukin 2(IL2) in T cell proliferation induced by soluble anti-CD3 antibodies. Apart from the synergy of anti-CD28 antibodies with phorbol myristate acetate and anti-CD3 antibodies, we found that anti-CD28 mAb were able to induce T cell mitogenesis in combination with an E rosette-blocking anti-CD2 antibody. In this report, we show that antibodies directed against different epitopes on the CD2 antigen can synergize with anti-CD28 mAb. Furthermore, we demonstrate that proliferation induced through the synergistic action of anti-CD28 mAb with anti-CD2 antibodies can be induced in the absence of accessory cells and is accompanied by the production of IL2 and the expression of IL2 receptors. We were unable to induce detectable Ca2+ mobilization through the simultaneous binding of anti-CD28 and anti-CD2 mAb. Taken together, these data show that IL2-dependent proliferation can be induced through the simultaneous binding of anti-CD28 and anti-CD2 antibodies, possibly through phosphatidyl inositol-independent pathways. The observations may provide further insight into the activation mechanisms of human T cells.     

Studies on the differentiation of T lymphocytes in sheep. III. Preliminary characterization of an antigen recognized by two anti-pan T-cell monoclonal antibodies.

ST-1a and ST-1b are monoclonal antibodies that selectively react with cells in the T-cell lineage of the sheep. Preliminary structural studies using radioimmunoprecipitation and sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) indicated that both ST-1a and ST-1b recognize an antigen of apparent molecular weight 67,000 and 60,000-65,000, under either reducing or nonreducing conditions. Differential expression of these 67,000 and 60,000-65,000 MW proteins was observed in T cells obtained from various anatomical compartments. Cortical thymocytes and efferent lymph lymphocytes expressed predominantly the 67,000 molecule, whereas a thymus cell fraction enriched for medullary thymocytes expressed mainly the 60,000-65,000 MW molecule. Both proteins were found in equivalent amounts in immunoprecipitates obtained from peripheral blood lymphocytes and lymph node lymphocytes. Peptide mapping studies indicated that 67,000 proteins of both ST-1a and ST-1b immunoprecipitates have significant homology in peptide composition. Sequential immunoprecipitation experiments clearly demonstrated that the antigens recognized by ST-1a and ST-1b antibodies are the same. On the basis of the size, tissue distribution and trypsin sensitivity of the antigen, together with cytofluorometry data, we suggest that the target antigen of ST-1a and ST-1b monoclonal antibodies is the ovine homologue of mouse Lyt-1 and human Leu-1.     

Moloney leukemia virus-induced cell surface antigen mimicry by monoclonal antibodies

We have investigated antigen-independent modulation of immune responses by monoclonal antibodies directed against both viral and nonviral antigens. BALB/c mice were immunized with monoclonal IgM (i.e. Ab1) specific for either Moloney murine leukemia virus-induced cell surface antigen (MCSA) or the hapten 2,4-dinitrophenyl (DNP). Injection with either Ab1 activated a functional idiotypic (Id) network as evidenced by production of both anti-Id (Ab2) antibodies and anti-anti-Id (Ab3) antibodies. A subset of induced Ab3 (designated Ab1), exhibited specificity for antigen (virus or DNP). In mice immunized with anti-Id antibodies (Ab2), production of Ab3 and Ab1′ was also observed. In the MCSA system, antibody-induced Ab1′ responses were effective in protecting mice from tumor development upon subsequent challenge with live virus. Furthermore, antigen-independent modulation of immunity to both viral and nonviral antigens was found to be thymus-dependent. Similar findings in other viral systems suggest that antibody-induced activation of Id networks may prove a viable alternative vaccine strategy that can elicit antigen-specific responses, and in some cases protection, in the apparent absence of exposure to antigen.     

Activation of human T lymphocytes by crosslinking of anti-CD3 monoclonal antibodies

The proliferation of human T lymphocytes induced by anti-CD3 monoclonal antibodies (mAb) is used as a model for antigen-induced activation via the T cell receptor-CD3 complex. Since both systems are accessory cell (AC)-dependent, an understanding of the role of AC in anti-CD3-induced proliferation may provide an understanding of physiological activation via the T cell receptor. Previous work has implicated receptor crosslinking as an important AC function. To determine its necessity in anti-CD3-induced lymphocyte proliferation, we prepared highly purified T lymphocytes and found that these cells did not respond to the anti-CD3 mAb UCHT1, either alone or with interleukin 1 (IL1), interleukin 2 (IL2), or tetradecanoyl phorbol acetate (TPA). However, the response, as measured by appearance of IL2 receptors and proliferation, was restored by crosslinking with immobilized goat anti-mouse antibodies (GAM) and did not require the addition of IL1, IL2, or TPA. Thus, crosslinking of CD3 receptors was a sufficient signal for proliferation of these cells. Cyclosporine A (CsA) inhibited the activation induced by immobilized UCHT1. Since macrophages are the principle targets of CsA-mediated suppression of mitogen-induced proliferation, but macrophages do not participate in the response to immobilized anti-CD3, this may indicate that CsA was inhibiting crosslinking or a signal generated by it.     

Studies on the differentiation of T lymphocytes in sheep. II. Two monoclonal antibodies that recognize all ovine T lymphocytes.

Two mouse monoclonal cytotoxic antibodies (ST-1a and ST-1b) recognize an antigen present on the large majority of thymocytes and all T cells in the periphery, but not B cells or other haemopoietic cells in sheep. Examination of frozen sections of various fetal tissues revealed that the cells expressing this antigen first appeared in the thymus, and these cells markedly increase in numbers in the peripheral lymphoid tissues after mid-gestation. Large accumulations of positive cells were located in the paracortex of lymph nodes, the periarteriolar lymphoid sheath of the spleen, and interfollicular areas of jejunal Peyer's patches, all of which are known to be T-dependent areas. Treatment of lymphocytes with ST-1a and complement resulted in the abrogation of T-proliferative responses, but the response to a B-cell mitogen, lipopolysaccharide, was not reduced. Neither ST-1a nor ST-1b cross-reacted to lymphocytes obtained from other species of animals (man, monkey, mouse, rat, guinea-pig, chicken, frog, pig, horse, goat and cattle). Based on these findings, it was concluded that the expression of the antigen recognized by ST-1a and ST-1b is restricted to the T-cell lineage of sheep, and that all ovine T cells express this antigen. Furthermore, ST-1a and ST-1b were determined to recognize the same antigen by reciprocal blocking experiments.     

Anti-VH antibodies interfere with antigen binding by human T lymphocytes.

The effect of antisera against a VH fragment have been investigated in several T cell proliferative assay systems. Anti-VH antisera raised in sheep, rabbits and chicken induced profound inhibition of PPD stimulated lymphoproliferation. Likewise were both mixed lymphocyte reaction (MLR) and autologous mixed lymphocyte reaction (AMLR) severely hampered while stimulation induced by mitogens was only minimally affected. Specificity testing indicates that the inhibiting antibodies in these experiments are not directed against native immunoglobulin determinants but rather against determinants specific for the VH fragment. These results thus support the notion that T cells express VH antigens and that these antigens are part of or closely associated with the antigen receptor on human T lymphocytes.