Salivary
secretory IgA (
sIgA) has been shown to react with a group of heat shock
mannoproteins preferentially expressed on yeast cells grown at 37 degrees C. Since at this temperature C. albicans can induce germ tubes, we explored the role of germ tube induction on human salivary
sIgA reactivity in both germinative and agerminative C. albicans strains, in an attempt to investigate whether the germ tube expressed the heat shock
mannoproteins reactive with
sIgA. The reactivity with
sIgA of the agerminative strain, grown at 25 and 37 degrees C for different times, was measured spectrofluorometrically and was fairly constant with time. Yeast cells grown at 37 degrees C tended to be more reactive than those grown at 25 degrees C. In contrast, when compared with the yeast cells of the germinative strain grown at 25 degrees C, there was a statistically significant decrease in reactivity with
sIgA during germ tube formation. Serum
IgA and
IgG did not show statistically significant changes in reactivity with C. albicans during germination, suggesting differences in reactivity with C. albicans cell wall
antigens between mucosal and systemic humoral responses. Cell wall
mannoproteins of molecular masses > 60 kDa were characterized by Western blotting as responsible for the decrease in
sIgA reactivity observed in the germ tube, and the fall in
sIgA reactivity was related to the release of cell wall
mannoproteins into the culture medium. The release of these
mannoproteins may be a mechanism whereby C. albicans avoids the action of
sIgA, and it may play an important role in the post-parasite relationship in
oral candidiasis.