Resident salivary gland macrophages function as accessory cells in antigen-dependent T-cell proliferation

The function of salivary gland macrophages in the induction of local immunity in secretory organs was investigated in Fischer 344 rats. Macrophages obtained from dispersed submandibular gland (SMG) cells were characterized and examined for their ability to present antigen to T cells. Populations of SMG-adherent cells contained approximately 80% macrophages, of which 46-62% were I-A+ cells. These numbers were from five to 10-fold greater than the I-A+ cells in macrophage populations from peritoneal exudates (5-11%). SMG macrophages functioned effectively as antigen-presenting cells. Antigen presentation was antigen specific, macrophage dose dependent and inhibitable by monoclonal anti-I-A antibodies. These studies suggest that a functional salivary-gland immune-response pathway exists that can function independently of a gut-associated lymphocyte-homing mechanism.