T cell activation by antigen-presenting cells from lung tissue digests: suppression by endogenous macrophages.
Parechymal cells (PC) were prepared by digestion of perfused, lavaged rat lung in a mixture of collagenase and DNase, and harvested on a discontinuous percoll gradient. The process yielded on average 1.0 X 10(8) viable cells/gram tissue. PC were pulsed with soluble antigen, and tested for their capacity to trigger antigen-specific activation of immune T-cells in vitro, or to replace adherent accessory cells necessary for Concanavalin A (Con A)-induced T-cell proliferation. Unfractionated PC exhibited only minor antigen-presenting cell (APC) activity. However, removal of adherent or FcR-positive cells unmasked substantial APC activity. Subsequent experiments indicated that the majority of the APC banded at the top of the percoll gradient (density less than 1.048 g/ml). The same cell preparations substituted for adherent accessory cells in Con A- activation of T cells, suggesting capacity to secrete soluble factors such as interleukin-1 (IL-1) as well to present antigen. The PC preparation also contained T-cells, which were refractory to Con A stimulation unless endogenous adherent cells were first removed. Collectively, these data suggest the presence of non-adherent, FcR-negative, low density accessory cells in the lung parenchyma, capable of both APC activity and soluble factor production. Their T-cell-activation functions appear to be down regulated by endogenous adherent, FcR-positive cells. It is speculated that the accessory cells in these lung preparations may be dendritic cells, the activity of which is subject to inhibition by macrophages.
D000818:Animals; D000938:Antigen-Presenting Cells / Q000276:immunology*; D002469:Cell Separation; D002499:Centrifugation, Density Gradient; D003208:Concanavalin A / Q000494:pharmacology; D005260:Female; D007108:Immune Tolerance; D008168:Lung / Q000166:cytology*; D008213:Lymphocyte Activation; D008264:Macrophages / Q000276:immunology*; D051381:Rats; D011919:Rats, Inbred Strains; D013601:T-Lymphocytes / Q000276:immunology*
D003208:Concanavalin A