We showed that hydrophilic C. albicans yeast cells adhere
specifically to macrophages located in the splenic marginal
zone and in the subcapsular and medullary sinuses of peripheral
lymph node tissue of mice (10, 14, 21). The specific
adherence can be demonstrated for the spleen and lymph node
tissues by an ex vivo assay and by in vivo analysis for splenic
tissue. We also showed that the mannan portion of the
phosphomannoprotein, designated Fr.II, isolated from yeastform
C. albicans cells by 3-mercaptoethanol (2-ME) extraction
and concanavalin (ConA)-agarose affinity chromatography,
contained the adhesins responsible for attachment to macrophages
in both types of tissues (21).
It was recently reported that the factor 6 antigen of serotype
A strains of C. albicans plays a role in fungal adherence to
epithelial cells (30, 31). Chaffin et al. (8) compared the
adherence properties of a cell surface C. albicans mutant with
those of wild-type C. albicans and suggested the importance of
cell wall mannan, especially P-1,2-linked oligomannosyl residues.
In accordance with these findings, Li and Cutler (28)
identified one adhesin site on the acid-labile portion of the
mannoprotein as a 1-1,2-linked tetramannosyl residue. However,
in both of the latter studies, the results indicated that
additional adhesins were on the mannoprotein.
To define other adhesin sites in the phosphomannoprotein
complex involved in adherence of C. albicans to the marginal
zone of the mouse spleen, we isolated an acid-stable mannoprotein
fraction from a serotype B strain of C. albicans and
examined its adhesin activity. We report that the acid-stable
mannoprotein fraction shows strong adhesin activity but is
devoid of epitopes for factors 5 (36) and 6 (26) or for antigen