Anti-Tn human monoclonal antibodies generated following active immunization with partially desialylated ovine submaxillary mucin.

Partially desialylated ovine submaxillary mucin plus an immunological adjuvant has been used by us to induce a humoral immune response to Tn antigen and sialylated Tn in colon cancer patients at risk of recurrence. Peripheral blood lymphocytes were purified from one of these patients with a high IgM titer reactive with Tn antigen transformed with Epstein-Barr virus and subsequently fused with a human-mouse heteromyeloma cell line, HMMA2.11TG/O. Clones were screened and subcloned using an enzyme-linked immunoassay and four stable IgM-secreting clones were tested for reactivity with a variety of natural and synthetic antigens, paraffin-embedded colon carcinomas and normal colonic mucosa to determine their specificity. Four human IgM monoclonal antibodies reactive predominantly with Tn antigen were produced and shown to react with a mucinous human colon carcinoma cell line, LS-174T, and with paraffin-embedded human colon carcinomas. We conclude that modified ovine submaxillary mucin is an effective vaccine for generating a humoral immune response directed to Tn antigen present on human colon cancer.