Immunobiology of the oral mucosa in the mouse

The incidence of immunoglobulin (Ig)-synthesizing cells, Thy 1-positive cells and macrophages in the murine oral mucosa was investigated. Immunofluorescence studies of frozen tissue sections showed that IgA-, IgM- and IgG-containing cells and Thy 1-bearing cells were closely associated with the minor salivary glands. A quantitative analysis was then undertaken using single cell suspensions of the tissue. After mechanical disruption or enzymatic digestion of the mucosa, lymphoid cells were recovered almost exclusively from the mucosa of the posterior soft palate where we observed a dense accumulation of minor salivary glands. Thy 1-bearing cells were found at a higher frequency (25% of recovered cells) than membrane Ig-positive B lymphocytes (6-7%) in these suspensions. Cytoplasmic Ig+ cells accounted for about 6% of recovered cells, whereas plaque-forming cells (Ig-secreting cells) occurred at the same frequency as in the spleen (0.1%). Plasma cells of the IgA and IgM isotypes predominated over IgG-secreting cells (A:M:G ratio = 1:1:0.2); this distribution did not directly correlate with the isotype distribution of salivary Igs (A:M:G ratio = 1:0.003:0.07). In addition, about 10-14% of the cells in our preparations were esterase-positive mononuclear cells. Present data indicate that the murine oral mucosa contains both effector and regulatory cells required for the development and expression of local antibody responses.