ACCESSORY FUNCTION OF ALVEOLAR MACROPHAGES FROM PATIENTS WITH MILIARY TBC AND CAVITARY TBC

Alveolar macrophages are believed to be important in initial mycobacterial con¬tainment and for activation of the cellular immune response. There is substantial controversy about the ability and efficiency of alveolar macrophages to serve as accessory cells for T cell responses to antigen and mitogens. Generally, accessory function is one way antigen presenting cells generating sufficient secondary signals for optimal T-cell proliferation and IL-2 production. On the contrary, alveolar mac¬rophages (AM) are inferior accessory cells in comparison to monocytes whereas in TBC accessory function of AM seems to be increased. Methods: we compared the accessory index of AM and peripheral blood mono¬cytes (PBM) of patients with miliary active TBC (n = 19), active cavitary TBC (n = 10), and hypersensitivity pneumonitis (HP) (n = 12), by employing the histoincompatibility-insensitive Jurkat cells as indicator cells. Results: compared with the controls (1.07 ± 0.2) AMs of all groups with the exclusion of TBC cavitary exhibited significantly increased accessory functions (miliary TBC: 3.7 ± 2.9; HP: 3 ± 2). Only in HP, accessory index of PBM was significantly increased compared with controls (3 ± 1.3 and 1.3 ± 0.5 respectively). AMs from patients with TB, and HP express the costimulatory molecule CD80 on their surface and anti-CD80 antibodies inhibited the IL-2 release of Jurkat cells in this system to 61 db 25%. Coclusions: our data demonstrate that AM from patients with miliary TBC have the capability to act as competent accessory cells and that the reported accessory function of these cells is at least in part mediated by the expression of CD80.