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Macrophages in efferent lymph of sheep and their role in lectin-induced lymphocyte blastogenesis
Very low numbers (3.9 +/- 3.0/10(5) cells) of macrophages (cells with intense cytoplasmic staining for nonspecific esterase) were found in seven popliteal lymph samples taken at surgery from 6 sheep. 67% of these cells were phagocytic for latex beads. Dose response and limiting dilution experiments indicated that efferent lymph lymphocytes responded to concanavalin A and pokeweed mitogen when at least 10 macrophages/10(5) cells were present, but macrophages appeared not to be necessary for phytohemagglutinin responses. Further depletion of macrophages from efferent lymph lymphocytes by nylon wool columns almost abolished concanavalin A and pokeweed mitogen responses and reduced phytohemagglutinin responses by 67%. The responses to all mitogens were restored to near normal efferent lymph lymphocyte levels by addition of 1% adherent cells and were elevated to near normal cell levels by 5% adherent cells. These results indicate that macrophages are present in efferent lymph and that, despite their low numbers, they may be of functional significance in regulation of immune responses.
Very low numbers (3.9 +/- 3.0/10(5) cells) of macrophages (cells with intense cytoplasmic staining for nonspecific esterase) were found in seven popliteal lymph samples taken at surgery from 6 sheep. 67% of these cells were phagocytic for latex beads. Dose response and limiting dilution experiments indicated that efferent lymph lymphocytes responded to concanavalin A and pokeweed mitogen when at least 10 macrophages/10(5) cells were present, but macrophages appeared not to be necessary for phytohemagglutinin responses. Further depletion of macrophages from efferent lymph lymphocytes by nylon wool columns almost abolished concanavalin A and pokeweed mitogen responses and reduced phytohemagglutinin responses by 67%. The responses to all mitogens were restored to near normal efferent lymph lymphocyte levels by addition of 1% adherent cells and were elevated to near normal cell levels by 5% adherent cells. These results indicate that macrophages are present in efferent lymph and that, despite their low numbers, they may be of functional significance in regulation of immune responses.