Heterologous B-Cell Antisera May Detect Non-Ig, Non-HLA-DR Antigens

A heterologous antiserum (antiserum 7420) against B-lymphocyte antigen(s) was raised in a rabbit by immunization with peripheral blood lymphocytes from a patient with chronic lymphocytic leukaemia (CLL). After absorptions with pooled normal human serum, IgA, IgD, and IgM M-components, the fluorescein isothiocyanate-conjugated F(ab')2 fragments were prepared and further absorbed with normal peripheral blood leucocytes. The F(ab')2 fragments, studied in direct immunofluorescence, reacted with both normal and CLL B lymphocytes but not with T lymphocytes. Comparative studies with an HLA-DR antiserum showed that the antigen(s) detected by 7420 antiserum did not redistribute together with HLA-DR antigens in cocapping experiments, nor did the HLA-DR antiserum block the reaction of 7420 F(ab')2 fragments with B lymphocytes. The 7420 F(ab')2 fragments prcipitated detergent-solubilized B-cell membrane material with a molecular weight of around 40,000 and 150,000 daltons. The conclusion drawn is that the 7420 and HLA-DR antigens are different. The 7420 antigen was also shown to be different from classical HLA antigens, beta 2-microglobulin, surface immunoglobulin, the Fc receptor, and HC protein.     

Same Idiotypc of B-Lymphocyte Membrane IgD and IgM. Formal Evidence for Monoclonality of Chronic Lymphocytic Leukemia Cells

Idiotypic antisera were raised in rabbits against serum M-cnmponents in two patients with chronic lymphocytic leukemia (CLL) In one of the patients the leukemic cells had membrane-bound IgG. in the other IgM and IgD. The M-components were IgG and IgM. respectively. By immunofluorescence technique the CLL cells were shown to be positive when stained with idiotypic antiserum prepared against the corresponding M component, whereas normal lymphocytes, as well as cells from other CLL patients, were negative. These findings represent strong evidence for the monoclonality of the malignant B cells in CLL The fact that the CLL cells had membrane-bound Ig with the same idiotypic determinants as the corresponding serum M-component indicated that the latter had been synthesized and secreted by the malignant clone of B cells. In further experiments redistribution of membrane-bound Ig on CLL cells bearing both IgM and IgD was induced with idiotypic antiserum This indicated that IgM and IgD on the same cells share idiotypic specificity and therefore have the same variable region and. presumably, the same antibody specificity     

Concanavalin-A-binding Proteins on the Surface of Human Malignant and Normal Lymphocytes

The concanavalin-A-binding cell surface glycoproteins from normal and certain leukaemic human lymphocytes were radiolabelled and then solubilized with detergent, isolated by affinity chromatography on Con A insolubilized on agarose beads, and subsequently analysed by SDS-polyacrylamide gel electrophoresis. Leukaemic T cells from patients with Sezary syndrome were found to express major concanavalin-A-binding glycoproteins on their outer surface similar to those of normal T lymphocytes. Leukaemic B cells from patients with chronic lymphocytic leukaemia expressed Con-A-binding proteins similar to those of B-cell lines. HLA antigens were predominant among the major Con-A-binding proteins on the surface of the normal and the malignant T cells studied. Human Ia-like antigens, HLA antigens, and the cell surface immunoglobulins IgD and IgM represented the major Con-A-binding proteins on the B cells studied. beta 2-microglobulin was found associated with HLA antigens on both leukaemic and non-leukaemic T and B cells. The presence of additional Con-A-binding proteins expressed on the surface of the different cell types studied is discussed along with some physical characteristics of the human Ia-like antigens isolated.     

Relationships Between β2-Microglobulin and Alloantigens Coded for by the Major Histocompatibility Complexes of the Rabbit and the Guinea Pig

Treatment of rabbit and guinea pig lymphocytes with Fab' fragments of anti-beta2-microglobulin completely inhibited the cytotoxic effects of alloantisera to RLA or GPLA antigens, respectively. Aggregation of beta2-microglobulin on the lymphocyte surface by successive incubations with goat anti-beta2-microglobulin on the lymphocyte surface by successive incubations with goat anti-beta2-microglobulin and F(ab')2 fragments of rabbit anti-goat IgG also made rabbit lymphocytes resistant to lysis by anti-RLA, and guinea pig lymphocytes resistant to lysis by anti-RLA, and guinea pig lymphocytes resistant to lysis by anti-GPLA. The two kinds of pretreatment of guinea pig lymphocytes did not affect the cytotoxicity of antisera directed against guinea pig Ia antigens. These results in conjunction with previous findings in the mouse and in man suggest that beta2-microglobulin on the lymphocyte surface in mammals is generally associated with major serologically defined histocompatibility antigens but not with I-region-associated antigens.     

Stimulation of lymphocytes by allogeneic lymphocytes and lymphoblasts in the presence of anti-HLA antisera.

Anti-HLA alloantisera inhibit mixed lymphocyte responses in which normal lymphocytes are used as stimulator cells. These same antisera are unable to inhibit lymphocyte proliferative responses stimulated by lymphoblastoid cells from cultured lymphoid cell lines. They also fail to inhibit either the generation of cytotoxic effector cells by lymphoblastoid cells or lymphocyte-mediated cytotoxicity against the lymphoblasts. Although the number of HLA antigens on the surface of lymphoblasts is reported to be greater than on normal lymphocytes, the failure of alloantisera to inhibit lymphoblast-induced responses in vitro does not appear to be due to insufficient amounts of antiserum to react with the antigenic sites. Rather, the data are interpreted to suggest that antigens which are not HLA and are not closely associated with HLA on the lymphocyte membrane are responsible for the stimulation of allogeneic lymphocytes by lymphoblastoid cells. Although lymphoid cell lines are known to contain the genome of the Epstein-Barr virus, antisera against products of the viral genome fail to inhibit proliferative responses to lymphoblastoid cells, suggesting that these antigens do not directly participate in lymphocyte activation.     

Lymphocyte Associated β2-Microglobulin Studied by Crossed Radioimmunoelectrophoresis

A sensitive radioimmunoelectrophoretic assay was employed in the study of beta 2-microglobulin (beta2m) from human blood lymphocytes, allowing the detection of 2.5 pmol of beta2m corresponding to 3 x 10(6) lymphocytes. The intrinsic (amphiphilic) membrane proteins were solubilized and examined in crossed immunoelectrophoresis against rabbit antisera in the presence of non-ionic detergent. The beta2m associated precipitate was traced by post-electrophoretic incubation with 125I-labelled antibodies to beta2m and autoradiography. A polyspecific rabbit antiserum to human lymphoid cells retained its capacity to precipitate lymphocyte beta2m after absorption with isolated beta2m (on an immunosorbent column), showing that lymphocyte beta2m is complexed to other molecules. No free beta2m was found on lymphocytes when examined against the absorbed antiserum to human lymphoid cells in an intermediate gel and anti-beta2m in a reference gel.     

Cellular Distribution, Purification, and Molecular Nature of Human la Antigens

Human Ia antigens were extensively purified (1390-fold increase in specific activity) in 32% yield from BRI 8 cells, a lymphoblastoid B-cell line. Purification was monitored by using allogeneic antisera arising by foetal-maternal stimulation. The product, a glycoprotein fraction, contained the Ia antigens, the HLA-A and -B antigens, and a glycoprotein of unknown function. The glycoprotein fraction was composed of four glycosylated polypeptides with molecular weights of 43,000, 39,000, 33,000, and 28,000, and beta2-microglobulin; no polypeptide was linked to another by disulphide bridges. The A and B antigens only were absorbed by antibody against beta2-microglobulin. The Ia antigens comprised one each of the 33,000 and 28,000 molecular weight glycosylated polypeptides noncovalently linked together. Thus, only these chains were absorbed by xenogeneic anti-Ia antisera and were cross-linked by dimethyl-3-3'-dithiobispropionimidate dihydrochloride. The dimeric molecule bound deoxycholate (0.26 g/g of protein) and, when solubilized in deoxycholate, has a molecular weight of 77,000. The Ia allo- and xeno-antigenic activities were labile to heating and proteolysis and are probably determined by the polypeptide structure. Xenogeneic specific anti-Ia antisera were raised in rabbits and mice by immunizing with the glycoprotein fraction. These antisera reacted with B lymphocytes and monocytes but not T lymphocytes and fibroblasts. Their Fab fragments blocked the cytotoxicity of the allogeneic antisera for B lymphocytes and were potent inhibitors of the mixed lymphocyte reaction.     

Some chronic lymphocytic leukemia cells bearing surface immunoglobulins share determinants with T cells.

One set of antigens is common to some chronic lymphocytic leukemia (CLL) cells bearing surface immunoglobulins (Ig) and normal T cells. Proliferating cells from thirty-eight patients were studied with four antisera recognizing normal human T but not B cells. These antisera were raised in rabbits against (a) Sezary cells, (b) blood lymphocytes from a patient with sex-linked agammaglobulinemia, (c) T lymphoblasts and (d) thymus cells. In four CLL cases, the cells expressed the receptor for sheep erythrocytes and lacked surface Ig. Cells from thirty-four CLL cases bore monoclonal surface Ig and did not bind sheep erythrocytes. Twelve out of these thirty-four cases of CLL had cells which were lysed by one or, more frequently, by the four anti-human T cell xenoantisera. By absorption experiments, one set of at least three antigens common to the cells of some of these CLL and T cells was defined. Depending on the patient, the cells can either carry one, some or all of the antigens of this set. However, it was also demonstrated by absorption that these cells lacked antigens particular to the T cell lineage, while the cells from T CLL cases carried both sets of antigens.     

Antibodies to surface IgM and IgD increase the expression of various class II antigens on human B cells

Antibodies to surface IgM and IgD were found to induce increased expression of class II antigens on normal and neoplastic human B cells within 24 h of stimulation. Antigens associated with different class II sub-locus genes (DC, DR and SB) were all found to be increased as determined by monoclonal antibodies (Leu-10 and B 3/4 for DC, D 1/12 for DR and MHM4 for SB-associated antigens). The increased expression of class II antigens was selective as anti-immunoglobulins failed to increase expression of other surface antigens such as B1 and beta 2-microglobulin. The effect of anti-mu and anti-delta could be blocked specifically by corresponding myeloma proteins suggesting that antibodies to surface IgM and IgD, respectively, were responsible for the effect observed. Moreover, antibodies to another surface antigen (B1) failed to induce such changes. Increased class II antigen expression appeared to be dependent on protein synthesis, and early changes in ion fluxes, but could not be elicited by membrane depolarization as reported in murine systems.     

Reduced rates of membrane turnover in lymphocytes from chronic lymphatic leukaemic patients

Lymphocytes in chronic lymphatic leukaemia (CLL) were found to release labelled antibodies against surface antigens at a slower rate than healthy cells and `escape from sensitization' was similarly prolonged in the abnormal lymphocytes. This suggests that membrane turnover in CLL lymphocytes is abnormally slow. The leukaemic cells can be provoked to turn over antisera more quickly by prior exposure to mitogenic stimulation and if nuclear material is used as a mitogen, membrane turnover will increase to a rate approaching that observed in normal lymphocytes. Once this acceleration has been achieved the leukaemic lymphocytes no longer react to an antiserum with specificity for leukaemic antigens and this result suggests that the leukaemic state of the CLL cell may be controlled by the surface membrane.     

Corticosteroids decrease the expression of beta 2-microglobulin and histocompatibility antigens on human peripheral blood lymphocytes in vitro.

The in vitro effect of two different glucocorticoids (prednisolone and dexamethasone) on the expression of beta 2-microglobulin and HLA-A-A, -B and -C-antigens on the surface of cultured lymphocytes was measured by quantitative immunofluorescence (flow cytofluorometry) and by a radioimmunoassay. Both antigens were found to be decreased, dexamethasone typically in a concentration of 10-6 mol/l causing a decrease in surface beta 2-microglobulin of 15% after an incubation period of 24 hr. The expression of two other lymphocyte surface antigens, Igm and Thy antigens, measured in parallel with beta 2-microglobulin and HLA antigens, was not affected by the same culture conditions. The steroid effect was not due to masking of the affected antigens, but was completely abolished by inhibition of protein synthesis.     

Cross-reacting Xenoantibodies to the Heavy Chain of H-2 and HLA-A, B Antigens: Serologic and Immunochemical Characterization

H-2 cross-reactive antibodies present in HLA xenoantisera were purified by absorption on and elution from murine cells. Antibodies isolated from one of these antisera, 78-E48, were found to mediate complement-dependent lysis of both human and murine lymphoid cells but not of Daudi cells or of human lymphoid cells coated with Fab2 fragments from a cow anti-human beta 2-microglobulin (beta 2 m) antiserum. In indirect immunoprecipitation analyses 78-E48 reacted only with proteins of approximately 45,000 and 12,000 MW present in NP-40 extracts of both human and murine lymphoid cells. Sequential precipitation experiments with rabbit anti-human beta 2 m and allo-anti-H-2Kk, Iak sera established that these proteins were in fact H-2 and HLA-A,B antigens. It was also found that 78-E48 reacted only with the heavy chain of HLA-A,b and H-2 antigens, since this eluate was unreactive with beta 2 m in a radioimmunoassay, and its capacity to immunoprecipitate the 45,000 and 12,000 MW proteins from human cell extracts was unaffected by prior reaction with purified human beta 2 m. These data show for the first time that H-2 and HLA-A,B antigens share properties that probably depend upon their teritary structure.     

Affinity Chromatography of β2-Microglobulin from Human Lymphocytes on Concanavalin-A-Sepharose

Beta2-microglobulin was extracted from human lymphocytes with nonionic detergent and separated by affinity chromatography on concanavalin-A-Sepharose. The retarded part of beta2-microglobulin is assumed to be associated with HLA antigens. Using a radioimmunoassay for beta2-microglobulin, the average number of presumably free beta2-microglobulin molecules and of presumably HLA-associated beta2-microglobulin molecules per lymphocyte was estimated to be 3.8 x 10(5) and 1.4 x 10(5), respectively.     

Human leukaemic T cells with complement receptors

Peripheral blood lymphocytes from a patient (EP) with lymphosarcoma cell leukaemia reported previously, had been found capable of forming sheep erythrocyte rosettes, reacting with T cell-specific antiserum and carrying surface immunoglobulins (Ig), IgM and IgD. It was suggested that the surface Ig were generated by leukaemic T cells due to activation of genes controlling synthesis of surface Ig. We here present evidence that these lymphocytes also carry complement receptors of B cells as detected by bovine erythrocyte–anti-bovine serum–complement complexes and by complement-coated zymosan. This study firmly establishes the presence of dual surface markers for T and B cells on the same leukaemic lymphocytes.     

A heterophile carbohydrate moiety common to mammalian IgM and erythrocytes detected by chicken IgM antibody.

Sequential treatment of chicken lymphocytes with normal sheep serum (NSS), chicken antiserum against sheep erythrocytes (SE) and formaldehyde results in rosette formation with SE. The identity of reactive components and the mechanism of rosette formation has been elucidated. The binding activity of NSS to chicken lymphocytes was ascribed to "natural" IgM anti-species antibodies. Subsequently, chicken IgM anti-SE antibody reacted with sheep IgM bound to the lymphocyte surface, and, following formaldehyde fixation, rosettes were formed by the addition of SE. The reaction of chicken anti-SE antibody was competitively inhibited with a hog blood group substance suggesting that it had binding specificity for a carbohydrate moiety which is shared by sheep IgM and SE. This specificity represented only a fraction of the bulk of chicken IgM anti-SE antibodies and was not manifested by antibodies of the IgG class. The analysis by the above-described "sandwich rosette assay" was extended to chicken antisera against horse, rat and mouse red cells and to normal sera from these species. Cross-matching of chicken antisera, with the normal sera and red cells from the tested species revealed a distinct pattern of cross-reactivities. These results imply that the saccharide epitope which is shared by IgM and red cells has a wide distribution between various mammalian species and may be classified as a new system of heterophile antigens.     

Contamination of anti-immunoglobulin reagents with antibodies to beta 2-microglobulin and other unrelated antigens. Effects on immunofluorescence staining of human lymphocytes.

IgG fractions from three of four rabbit antisera to Bence Jones proteins of chi-type were found to contain antibodies to beta 2-microglobulin and to stain 80%-100% of human blood lymphocytes by indirect immunofluorescence. Antibody fractions from these sera, which contained anti-beta 2-microglobulin but not anti-Ig, stained all lymphocytes, whereas the isolated anti-Ig antibodies (anti-chi) stained only a minor cell population. In both instances, the specificity of the staining was confirmed by absorption experiments. One antiserum to the constant half of lambda-type Bence Jones protein also contained antibiodies to beta 2-microglobulin and stained all lymphocytes. Four other anti-lambda reagents contained no antibodies to beta 2-microglobulin and stained at most about half of the lymphocytes. The antigen responsible for this staining is unknown. The isolated anti-immunoglobulin antibodies (anti-lambda) stained only 5%-10% of the lymphocytes. Antisera to serum IgG or its fragments were free of antibodies to beta 2-microglobulin and stained only 10%-25% of the lymphocytes. This staining was in all instances due to antibodies to human immunoglobulin. Five of eight undiluted sera from normal rabbits with no detectable antibodies to human immunoglobulin or beta 2-microglobulin stained 25%-60% of the lymphocytes. This staining rapidly disappeared on dilution.     

Analysis of cell-surface markers with staphylococcal protein A: fluorescence studies on mammalian lymphoid determinants.

Membrane antigens including different classes of immunoglobulins, transplantation antigens, beta2-microglobulin, T lymphocyte specific antigens, and virally determined surface components were investigated using fluorescein-labeled Staphylococcal protein A in combination with cytofluorometric studies. Lymphocytes of seven species: mouse, rat, guinea pig, pig, cow, monkey, and human, and of ten human lymphoma-derived lines were tested. Analysis of the differential expression of surface markers revealed a reproducible reaction of protein A with cell-surface Fc of IgG actively produced by lymphoid cells from human, monkey, guinea pig, and pig, and with passively attached IgG molecules in the form of antibodies, directed against cell surface antigens of all lymphoid cells tested. No surface Ig was detected on so-called T lymphocytes. The distribution of cell-bound Ig density among surface Ig-positive cells was found to be different depending upon the origin of the cells with regard to lymphoid organ; it was parallel among the lymphoma lines tested and on peripheral blood cells from human, monkey, and pig, although large variations in fluorescence intensity among individual cells and among the different lines were recorded. Beta2-microglobulin determinants were found equally well on enriched human T and B cells. Transplantation, and T lymphocyte-specific antigens were detected on the majority of the lymphoid cells and on a restricted population respectively.     

Monoclonal lymphocyte population in human plasma cell myeloma

To identify monoclonal bone marrow-derived (B) lymphocytes in human myelomatosis specific rabbit antisera were produced against idiotypic specificities on IgG-κ myeloma proteins from three patients. The antisera neither cross-reacted nor reacted with normal immunoglobulins. By indirect immunofluorescence surface immunoglobulins were demonstrated on 20–47% of peripheral blood lymphocytes from untreated patients after staining with idiotypic antiserum against the patient's own myeloma protein, but not after staining with other idiotypic antisera. The antisera also stained autologous plasma cells. The monoclonal surface Ig on myeloma lymphocytes was removed by trypsin and regenerated after incubation in serum-free medium. Myeloma protein was not adsorbed onto lymphocytes. It is concluded that monoclonal B lymphocytes belonging to the plasma cell myeloma clone are present in myeloma patients. There were few normal B lymphocytes in untreated patients.

During treatment the monoclonal lymphocyte population and the plasma cells content in bone marrow, as well as the concentration of monoclonal immunoglobulin in serum, decreased simultaneously. These findings were associated with other signs of clinical improvement.

     

Revised classification of the DLA loci by serological studies

Peripheral blood mononuclear cells from DLA typed dogs were treated with rabbit-anti-dog-beta 2-microglobulin and subsequently with goat-anti-rabbit-immunoglobulin in order to aggregate the DLA class I molecules on the cell membrane (lysostrip). Utilizing a panel of 70 defined DLA-A and DLA-B antisera, lymphocytes treated in this way showed resistance to complement dependent lysis with monospecific DLA-A sera only, whereas reactivity of DLA-B antisera was not blocked; on the contrary, complete lympholysis with each DLA-B antiserum was recognized. Thus, the DLA-B antigens, evidently not associated with beta 2-microglobulin, are designated as candidates for class II gene products. The different reactions of DLA-C antisera after lysostrip did not allow a precise assignment of this antigen series as yet.     

Immunological studies of trophoblast antigens: no evidence for human leucocyte antigen (HLA) linkage

Parental disparity for trophoblast-lymphocyte crossreactive (TLX) antigens may promote successful pregnancy. A TLX antigen system has been defined on peripheral blood lymphocytes by heteroantisera. More recently, we have reported additional activity against antigens on B lymphocytes alone termed trophoblast-B lymphocyte crossreactive (TBX) antigens. In the present study we have investigated ten TLX sera in order to determine if their target antigens are linked to the human leucocyte antigen (HLA) gene complex. The sera showed no selective activity when tested against target B lymphocytes from ten normal donors. Cytotoxic activity of TLX antisera against peripheral blood lymphocytes from six normal donors was not reduced when the class I HLA antigens of the target cells were blocked with a monoclonal antibody (PA 2.6). Similarly the cytotoxic activity of both TBX antisera against B lymphocytes from six normal donors was not decreased when class II HLA antigens were blocked by a monoclonal antibody (FMC 4). Within a family the cytotoxic activity of the TLX antisera was absorbed equally by lymphocytes from siblings who shared neither HLA haplotype. Antibody content in TLX and TBX antisera is not directed toward the classically defined HLA class I or class II antigens and is not linked to the HLA gene complex.