Serum blocking factors in bovine ocular squamous cell carcinoma demonstrated by inhibition of erythrocyte rosette augmentation

Blood leukocytes from cattle with bovine ocular squamous cell carcinoma (BOSCC) react with extracts of BOSCC, and blood leukocytes from cattle with cutaneous papillomas react with extracts of papillomas in the erythrocyte rosette (E-rosette) augmentation test. Sera from cattle with BOSCC, with cutaneous papillomas, and with ocular papillomas and sera from lesion-free cattle were tested for their ability to block antigen-induced E-rosette augmentation and E-rosette augmentation induced by phytohemagglutinin. Autologous serum from 16 BOSCC-affected cattle blocked E-rosette augmentation induced by BOSCC extract, and autologous sera from three cattle with cutaneous papillomas blocked E-rosette augmentation induced by papilloma extract. Sera from cattle with BOSCC did not block E-rosette augmentation induced by papilloma extract, nor did sera from cattle with cutaneous papillomas block BOSCC extract-induced E-rosette augmentation. Sera from cattle with BOSCC blocked BOSCC extract-induced E-rosette augmentation in some but not all allogeneic combinations. E-rosette augmentation was observed when blood leukocytes from all 12 BOSCC-affected and six control cattle were exposed to phytohemagglutinin. This reaction was blocked by autologous sera from 11 of the 12 BOSCC-affected cattle, from one of the three cattle with cutaneous papillomas, but from none of the three other cattle. Sera from BOSCC-affected cattle also blocked phytohemagglutinin-induced E-rosette augmentation in allogeneic combination, regardless of the tumor status of the donor of the leukocytes.