Antigenic modulation of pan-T-cell and T-cell subset-specific markers

The time course and extent of antigenic modulation induced by monoclonal antibodies OKT3, OKT4, OKT8, BE2, and BE3 was investigated. OKT3-induced antigenic modulation could be detected as early as after 3-hr incubation with the antibody and almost total removal of the OKT3-reactive antigen was seen by 42 hr. This modulation did not decrease the expression of T-cell antigens detected by OKT4 and OKT8. OKT3-modulated cells reexpressed the antigen after 42-hr incubation in OKT3-free media. BE3 (homologue of OKT1) also caused modulation of its surface antigen after 24-hr incubation. In contrast, OKT4 did not induce modulation even after 42-hr incubation with high concentrations of OKT4 antibody. Approximately 43% of the OKT8-reactive lymphocytes could be induced to modulate this antigen. A tumor-associated antigen present on neoplastic lymphocytes from patients with cutaneous T-cell lymphoma, recognized by monoclonal antibody BE2, also was not induced to modulate. These results suggest that antigenic modulation and the fate of the modulated antibody may be of importance to immunotherapeutic applications of these reagents.