Spherules in the serology of Coccidioides immitis. II. Complement fixation tests with human sera

Soluble and particulate spherule antigens fixed complement in tests with anti—C. immitis sera. However, the soluble antigen proved more active than the particulate one. Cross reactions were noted between the spherule antigens and anti—H. capsulatum and anti—B. dermatitidis sera. Following enzymatic treatment of the particulate preparation a soluble antigen was obtained which formed two bands with anti—C. immitis serum and one band with anti-H. capsulatum serum in an agar gel double diffusion test.