Chicken thrombocytes. Isolation, serological and functional characterisation using the fluorescence activated cell sorter

Different procedures for enrichment of peripheral blood leukocytes (PBL) from whole chicken blood have been compared in terms of the percentage yield of lymphocytes and thrombocytes. The yield of thrombocytes was low in the buffy coat cells of heparinised blood, but high in PBL enriched from heparinised blood over a Ficoll-Paque density gradient and in PBL prepared from citrated blood by either technique. The fluorescence activated cell sorter (FACS) has been used to separate thrombocytes from lymphocytes in PBL by sorting of the negative cells after staining with specific anti-T and anti-B cell sera (or anti-immunoglobulin). The sorted cells were more than 99% viable, more than 98% thrombocytes by antigenic and morphological criteria and did not respond in vitro to T and B cell mitogens. Absorption studies on a turkey anti-bursa cell serum (ABST) which is cross-reactive for B cells and thrombocytes (8) indicated that the cross-reactivity is attributable to two (or more) antibody specificities in the serum rather than to one antibody directed at shared determinants on the two cell types.

A monoclonal antibody against a surface antigen shared by human large granular lymphocytes and granulocytes

A monoclonal IgM antibody VEP13 was raised against a cell membrane antigen by immunizing BALB/c mice with a cell preparation enriched for human large granular lymphocytes (LGL). These cells are known to include the effector cells responsible for natural killer (NK) and killer (K) cell activity. By indirect immunofluorescence, VEP13 antibody reacted with 21.4 +/- 7.9% of peripheral blood lymphocytes (PBL) and more than 95% granulocytes but not with B lymphocytes, monocytes, erythrocytes, thrombocytes, thymocytes, and immature bone marrow cells. Cell suspensions enriched for T cells by means of E-rosetting using neuraminidase-treated sheep red blood cells contained 14.7 +/- 5.5% of VEP13+ cells. When PBL were treated with VEP13 antibody and complement, NK activity against a variety of target cells was greatly reduced and K cell activity was also strongly affected. Enrichment experiments of VEP13+ cells by means of the fluorescence-activated cell sorter revealed that all the NK activity resides in the VEP13+ fraction. This cell fraction was a homogeneous population of LGL. Studying the coexpression of various other antigens as defined by monoclonal antibodies, 84.6 +/- 4.6% of VEP13+ cells also expressed M1, 81.6 +/- 5.5% T10, 47.9 +/- 14.4% Leu 2a, 51.6 +/- 17.0% human Lyt-3, and 6.0 +/- 4.0% HLA-DR antigens. Leu 1, Leu 3a, and T6 antigens were found to be absent from VEP13+ cells. We conclude that VEP13 antibody should be helpful in determining LGL in peripheral blood as well as in tissue sections of tumor patients.

A monoclonal antibody against a surface antigen shared by human large granular lymphocytes and granulocytes

A monoclonal IgM antibody VEP13 was raised against a cell membrane antigen by immunizing BALB/c mice with a cell preparation enriched for human large granular lymphocytes (LGL). These cells are known to include the effector cells responsible for natural killer (NK) and killer (K) cell activity. By indirect immunofluorescence, VEP13 antibody reacted with 21.4 +/- 7.9% of peripheral blood lymphocytes (PBL) and more than 95% granulocytes but not with B lymphocytes, monocytes, erythrocytes, thrombocytes, thymocytes, and immature bone marrow cells. Cell suspensions enriched for T cells by means of E-rosetting using neuraminidase-treated sheep red blood cells contained 14.7 +/- 5.5% of VEP13+ cells. When PBL were treated with VEP13 antibody and complement, NK activity against a variety of target cells was greatly reduced and K cell activity was also strongly affected. Enrichment experiments of VEP13+ cells by means of the fluorescence-activated cell sorter revealed that all the NK activity resides in the VEP13+ fraction. This cell fraction was a homogeneous population of LGL. Studying the coexpression of various other antigens as defined by monoclonal antibodies, 84.6 +/- 4.6% of VEP13+ cells also expressed M1, 81.6 +/- 5.5% T10, 47.9 +/- 14.4% Leu 2a, 51.6 +/- 17.0% human Lyt-3, and 6.0 +/- 4.0% HLA-DR antigens. Leu 1, Leu 3a, and T6 antigens were found to be absent from VEP13+ cells. We conclude that VEP13 antibody should be helpful in determining LGL in peripheral blood as well as in tissue sections of tumor patients.

Antigenic heterogeneity of rat macrophages. A monoclonal antibody reacting only with alveolar but not with other types of macrophages

Hybridoma antibodies were produced by fusing spleen cells from mice immunized with rat alveolar macrophages (AM) with P3 x 63Ag8/653 myeloma cells. Some of the hybridomas were processed to achieve monoclonality. Reactivity was tested in an indirect membrane immunofluorescence assay. One of the monoclonal antibodies, called VEP6 antibody, reacted with rat AM but not with peritoneal or splenic macrophages and not with peripheral blood monocytes of this species. It was also unreactive with cells from thymus, bone marrow, non-adherent spleen cells, granulocytes and erythrocytes, but it reacted with thrombocytes. Corynebacterium parvum activated AM were slightly less reactive then 'resident' AM, as determined in a fluorescence activated cell sorter. The VEP6 antigen was studied in polyacrylamide gel electrophoresis after immunoprecipitation from 125I-surface-labelled-macrophage NP40-lysates. Four specific radioactive bands were seen in the precipitates corresponding to molecular weights of 31, 33, 35 and 37,000. A slurred band was seen in this molecular weight range when immunoprecipitates of surface labelled thrombocytes were analysed. This study confirms the heterogeneity of macrophages by showing that certain antigens may be expressed only on a subpopulation of macrophages.

Short time bleaching of fluorescein isothiocyanate. A possible parameter for the specific binding of conjugates in immunofluorescence

The fluorescence kinetics of fluorescein isothiocyanate (FITC)-antibody conjugates during short (0.01 sec) laser excitations were analyzed for possible information about the immunological specificity of binding to antigenic substrates in direct immunofluorescence assays with antigen-coated Sephadex beads. First results of these investigations suggest marked differences in the bleaching characteristics of specifically and nonspecifically bound FITC conjugates: FITC-anti-bovine serum albumin (BSA) and FITC-anti-rabbit immunoglobulin (Ig) were found to fade significantly more slowly when bound to the respective homologous antigen (anti-BSA to BSA, and anti-rabbit Ig to rabbit Ig) as compared to nonspecifically adherent anti-BSA to rabbit Ig, and anti-rabbit Ig to BSA. Possible implications of these data for discrimination of nonspecific staining in immunofluorescence are discussed.