Mononuclear and IgA-containing cells in the lacrimal gland of germ-free and conventional rats

Abstract

Mononuclear cells in the lacrimal (exorbital) glands of five germ-free, five ex-germ-free, and five age-matched conventional rats were counted by light microscopy. Tissues from these rats were also examined by electron microscopy. IgA-containing plasma cells were counted by immunofluorescence microscopy in the lacrimal glands of five germ-free and five conventional rats. The median number (and range) of mononuclear cells per ten high-power fields was 25 (14–28) in germ-free rats, 33 (32–43) in ex-germ-free rats, and 41 (36–50) in conventional rats. The median number (and range) of IgA-containing plasma cells per ten high-power fields was two (0–5) in germ-free and 44 (29–72) in conventional rats. The differences in the numbers of mononuclear cells in the lacrimal glands of germ-free as compared with ex-germ-free and with conventional rats were statistically significant ( P < 0·004). The difference between the numbers of IgA-containing plasma cells in germ-free as compared with conventional rats was also statistically significant ( P < 0·004). Electron microscopy revealed that the mononuclear cells in all groups of rats consisted of macrophages and lymphocytes. These observations suggest that the number of mononuclear cells, and particularly IgA-containing plasma cells, in the rat lacrimal gland can be increased by systemic and/or local immunologic stimulation.