title: Human alveolar macrophages inhibit receptor-mediated increases in intracellular calcium concentration in lymphocytes.
abstract: Prior studies have demonstrated that human alveolar macrophages (AM) are suppressive of lymphocyte function, through the mechanism of inhibition is unclear. In the current study, human AM inhibited receptor-mediated increases in intracellular calcium concentration ([Ca2+]i) in T cells, natural killer cells, and B cells. This effect was produced by either live or fixed AM, while peripheral blood monocytes caused a minimal reduction in [Ca2+]i. The inhibitory effect of AM was seen following 1 to 2 h of incubation with lymphocytes, was complete at 16 h, and did not affect ionomycin-mediated [Ca2+]i. Inhibition of [Ca2+]i by AM correlated with suppression of T-lymphocyte proliferation and cytotoxic T-lymphocyte activity in response to alloantigen and Staphylococcus A-induced immunoglobulin production. Our findings suggest that a membrane signal on AM is capable of inhibiting receptor-mediated signal transduction in lymphocytes and that this is likely a major mechanism by which immune responses are downregulated in the alveolus.
authors.affiliation: Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas 75235-9034.
authors.forename: W C
authors.initials: WC
authors.lastname: Yarbrough
authors.forename: D S
authors.initials: DS
authors.lastname: Wilkes
authors.forename: J C
authors.initials: JC
authors.lastname: Weissler
mesh_terms: D002118:Calcium / Q000378:metabolism*; D005434:Flow Cytometry; D006801:Humans; D008214:Lymphocytes / Q000378:metabolism*; D008264:Macrophages / Q000378:metabolism*; D011650:Pulmonary Alveoli / Q000166:cytology / Q000276:immunology*; D011956:Receptors, Cell Surface / Q000378:metabolism*; D015398:Signal Transduction
chemical_list: D011956:Receptors, Cell Surface; D002118:Calcium