Pharmacological administration of granulocyte/macrophage-colony-stimulating factor is of significant importance for the induction of a strong humoral and cellular response in patients immunized with recombinant carcinoembryonic antigen.

Eighteen colorectal carcinoma patients without macroscopic disease after surgery were immunized using recombinant (r) human (h) carcinoembryonic antigen (CEA) with (n=9) or without (n=9) the addition of soluble granulocyte/macrophage-colony-stimulating factor (GM-CSF). The dose of rhCEA per immunization was 100 microg (n=6), 316 microg (n=6) or 1000 microg (n=6). rhCEA was given s.c. on day 1 and 80 microg/day of GM-CSF s.c. on days 1-4. The schedule was repeated six times during a period of 9 months. All patients in the GM-CSF group developed a strong rhCEA-dose-dependent IgG antibody response while only one-third of the non-GM-CSF patients mounted a weak antibody response. All patients (9/9) in the GM-CSF group developed a strong rhCEA-specific proliferative T cell response as well as type I T cells (interferon gamma secretion). In 45% of the patients also a weak type II T cell response (interleukin-4 secretion) was evoked. Both MHC-class-I- and -II restricted rhCEA-specific T cells were noted. A specific cellular response (proliferation and/or cytokine secretion) against native hCEA could be found in 8/9 patients in the GM-CSF group, although at a significantly lower level than against rhCEA. In the non-GM-CSF group a weak rhCEA-specific T cell response was induced. Three patients had a proliferative response, 4 patients type I T cells and 6 patients type II T cells. No signs of autoimmune reactions were noted. Local pharmacological administration of GM-CSF seemed to be a prerequisite for the induction of a strong immunity against baculovirus-produced hCEA protein. However, the cellular response against native CEA was of a significantly lower magnitude.