The properties and functional activity of non-lymphoid cells from bovine afferent (peripheral) lymph

Abstract

Following prescapular lymphadenectomy, the cellular composition of afferent (peripheral) lymph from eight out of 13 calves in which the afferent and efferent lymphatic ducts had anastomosed was examined using monoclonal antibodies (mAb) specific for bovine lymphoid populations. Afferent lymph leucocytes (ALL) consisted of around 50% T lymphocytes, of which 35% and 14% expressed BoT4 and BoT8, respectively, 20-25% B lymphocytes and 23% non-lymphoid cells. When populations of non-lymphoid cells were prepared from ALL by adherence to gelatin-plasma-coated flasks, 81% contained alpha-napthyl acetate esterase (ANAE) and 70% were phagocytic, whereas the non-adherent population contained around 5% of these cell types, the cells being largely non-phagocytic and negative for ANAE. Following purification of non-lymphoid cells on the fluorescence-activated cell sorter (FACS) using IL-A22 (mAb detecting macrophages and polymorphonuclear leucocytes, PMN), only 72% of the positive cells contained ANAE, 19% were phagocytic, and 84% expressed Fc1 receptors. While the ALL depleted of IL-A22+ cells could not proliferate in the presence of specific antigen in culture, the addition of purified monocytes from peripheral blood leucocytes (PBL) or IL-A22-positive ALL to macrophage-depleted PBL or IL-A22-negative ALL promoted proliferative responses to specific antigens. Similar populations of non-lymphoid cells stimulated mixed leucocyte reactions (MLR) in allogeneic combinations. When these non-lymphoid cells were pulsed with specific antigens prior to addition to autologous PBL or ALL in culture, normal or gamma-irradiated but not glutaraldehyde-fixed cells from PBL or ALL induced proliferation and immunoglobulin (Ig) synthesis in responder cells. Proliferation was depressed in cultures containing mAb detecting BoT4, MHC class II antigens and a mAb which detected non-lymphoid cells in PBL; Ig synthesis was inhibited only by anti-class II mAb. Monocyte-depleted PBL or IL-A22-negative ALL responded specifically to autologous antigen-presenting cells which had been pulsed with the original immunogen and not other antigens.