Porcine alveolar macrophages: poor accessory or effective suppressor cellsfor T-lymphocytes

Porcine Alv-Mempty set from bronchoalveolar lavages were tested for their f unction in an in vitro foot-and-mouth disease virus (FMDV)-specific lymphop roliferative recall response. The Alv-Mempty set were seen to be poor acces sory cells when compared with peripheral blood monocytes. This poor capacit y was evident despite an efficient expression of SLA-DR region antigens, an d other costimulatory adhesion molecules. It was noted that Alv-Mempty set secrete relatively little interleukin 1 (IL-1 beta), with or without LPS in duction, even though mRNA for the cytokine could be detected. In contrast, blood monocytes with their effective accessory activity were potent secreto rs of IL-1. Although this IL-1 beta would be important with respect to the accessory capacity of monocytic cells, it was noted that the absence of bio active IL-1 from the Alv-Mempty set cultures was not solely responsible for their poor accessory function. In fact, the Alv-Mempty set produced factor s which not only inhibited IL-1 bioactivity, but were also responsible for a clear suppression of lymphoproliferation. This suppressor activity was de pendent on the type of monocytic cell present in the culture. being more pr ominent when "scavenger" phagocytes were present. Thus, the major role of A lv-Mempty set is not as an accessory cell akin to monocytes, but as both a scavenger cell, related to Mempty set derived from monocytes in the absence of inflammatory signals, and an immunoregulatory cell. (C) 2000 Elsevier S cience B.V. All rights reserved.