The major goal of this research is to delineate certain parameters of the antibody response to squamous carcinomas of the head and neck regions and to delineate the patterns of expression of carbohydrate sequence tumor-associated antigens of the carcinoma cells. Using frozen sections of tissues of known ABO blood type, the blood group antigen compositions of head and neck squamous carcinoma tissues and normal epithelial tissues were examined by the immunohistochemical method of Pankow et al. (J. Cytochem. Histochem., in press). Antigens investigated included A, B, H, T, I, i, Lea, Leb, peanut agglutination reactive (PNA), and sialic acid (SA). Antiserum to mannose was used as a probe for mannose (Man) residues and monoclonal antibodies directed to the Lex and type 1 chain determinants. ABH expression for normal epithelia corresponded to that expected for the ABO blood type, while partial or complete loss of A, B, or H antigens was observed in eight of 10 tumor tissues. DMan, T, and Lex antigens were observed in 3/4, 2/5, and 1/3 of the tumors examined, respectively, but were lacking on normal epithelia. I, i, and PNA antigens were detected in all normal epithelia and three of five tumors examined. Type 1 chains were observed in all normal epithelia and two tumor tissues. Although present on normal tissues, SA levels were greater in tumor tissues. These results show that head and neck squamous carcinoma tissues may demonstrate altered blood group and blood group precursor antigen expressions due either to antigen deletion, alteration, or accessibility to reactivity with antibody reagents. In additional studies, we have used a sensitive fluorophore enzyme-linked immunoassay to quantitate Igs intrinsically present in squamous carcinoma tissues. The assay has also been used to provide a quantitation of the blood group antigens in the tumor sections by removal and measurements of the antibody reactive to the tissue antigens. (IT)