concanavalin-a and leucine-methyl-ester

The effects of injection of linoleic acid into C57Bl/6 mice on hematopoietic and immunological parameters were examined. Administration of linoleic acid stimulated hematopoiesis as it increased spleen weight and cellularity, increased the number of bone marrow and splenic granulocytic-monocytic progenitor cells, and increased the colony stimulating factor activity in the serum of the treated mice. Associated with the hematopoietic stimulation in linoleic acid-treated mice was a decline in the spleen cell blastogenic responses and the appearance of bone marrow suppressor cells which were inhibitory to normal spleen cell blastogenesis. The linoleic acid-induced bone marrow suppressor cells resembled cells of the monocyte lineage in that they were sensitive to treatment with L-leucine methyl ester, partially sensitive to treatment with anti-Ia antibodies and complement, and their suppressor activity was minimized by indomethacin, a prostaglandin synthesis inhibitor. These results suggest that administration of linoleic acid results in hematopoietic stimulation and, concurrently, in the appearance of suppressor cells in the bone marrow. The bone marrow suppressor cells resemble immature cells of the monocyte lineage and appear to mediate their suppressive effects through the production of prostaglandins.

Topics: Animals; Bone Marrow Cells; Colony-Forming Units Assay; Colony-Stimulating Factors; Concanavalin A; Hematopoiesis; Histocompatibility Antigens Class II; Immune Tolerance; Indomethacin; Injections, Subcutaneous; Leucine; Linoleic Acid; Linoleic Acids; Male; Mice; Mice, Inbred C57BL; Spleen; T-Lymphocytes, Regulatory

We investigated the lysis of fresh human solid tumor cells by peripheral blood T lymphocytes in the presence of lectins and anti-CD3 monoclonal antibodies (mAb). Addition of certain lectins (Con A, PHA, or WGA) directly into the 4-hr 51Cr-release assay caused significant lysis of (P less than 0.001) noncultured solid tumor targets by enriched populations of granular lymphocytes (GL). Significant levels (P at least less than 0.001) of Con A- or PHA-dependent solid tumor lysis by GL-enriched lymphocytes were observed in 32 of 39 donors (82%) and 14 of 20 donors (70%), respectively. In contrast, the addition of other lectins (PNA, PWM, or LPS) or anti-CD3 mAb did not cause cytotoxicity. The levels of Con A-dependent lysis were comparable to those of interleukin 2 (IL-2)-induced lysis by Leu 11b+ natural killer (NK) cells. The presence of lectins at the effector phase, but not of recombinant IL-2 (rIL-2), was required for the lysis of solid tumor targets. Both Con A-dependent and rIL-2-induced lysis were totally inhibited by treatment of the effector cells with the lysosomotropic agent L-leucine methyl ester (LeuOMe). Effector cells responsible for Con A-dependent lysis of solid tumors expressed T3 (CD3), T8 (CD8), and Leu 7 antigens, but lacked T4 (CD4) and Leu 11 (CD16) antigens as determined by both negative and positive cell selection studies. Con A-dependent lysis was inhibited at the effector phase by anti-CD3 (OKT3 or anti-Leu 4) or anti-CD2 (OKT11) mAb. On the basis of their phenotype (Leu 7+ CD3+ CD8+ CD16-), we hypothesize that these effector cells may contain a population of cytotoxic T cells (CTL) generated in vivo against autologous modified cells that can lyse fresh solid tumor target cells under conditions where the recognition requirements for the CTL are bypassed by lectin approximation.

Topics: Antibodies, Monoclonal; Antigens, Differentiation, T-Lymphocyte; Antigens, Surface; Concanavalin A; Cytotoxicity, Immunologic; Humans; Immunity, Cellular; Interleukin-2; Killer Cells, Natural; Leucine; Neoplasms; Phytohemagglutinins; T-Lymphocytes

Cell separation and enrichment techniques were employed to isolate three distinct leukocyte subpopulations present in channel catfish (Ictalurus punctatus) peripheral blood. Surface immunoglobulin-positive (sIg+) and sIg- lymphocytes were separated by an indirect "panning" technique employing monoclonal antibodies reactive with channel catfish Ig. A third cell population composed of macrophages was isolated by adherence to baby hamster kidney cell microexudate-coated surfaces. Functional features of these three subpopulations were assessed by in vitro mitogenic responses to lipopolysaccharide (LPS) and concanavalin A (Con A). The results that were obtained indicated that the sIg+ cells responded only to LPS stimulation regardless of the presence or absence of macrophages. The sIg- subpopulation, however, responded to neither LPS nor Con A unless macrophages were present, in which case responses were obtained to both mitogens. The accessory cell nature of the macrophages was shown by experiments utilizing fixed numbers of one cell type mixed with varying numbers of another cell type. Furthermore, the accessory cell function was abrogated by passage through Sephadex G-10 and preincubation with L-leucine methyl ester. These studies provide further evidence that teleosts not only contain B and T cells akin to those in mammalian systems, but contain accessory cells (macrophages) as well.

Topics: Animals; Cell Separation; Concanavalin A; Fishes; Immunosuppressive Agents; Leucine; Leukocytes; Lipopolysaccharides; Lymphocyte Activation; Phylogeny