Enhancement of primary and secondary responses to sheep red blood cells and influenza virus in BALB/c mice by recombinant human interleukin-2

Treatment with recombinant human IL-2 (rIL-2) is being investigated as a new modality for the control of minimal residual disease in conjunction with autologous bone marrow transplantation for a variety of malignant hematological disorders and certain solid tumors. In investigating the functional role of rIL-2 in T cell dependent humoral immune responses, we determined the level of IgG, IgM, and total antibodies activity in BALB/c mice, with or without rIL-2 administration, before primary or secondary immunization with sheep red blood cells (SRBC) or influenza virus A/PR8/34 (H₁N₁). Our results show the beneficial effect of pretreatment with rIL-2 in enhancing primary and secondary humoral immune responses to SRBC (p < 0.05) and possibly to influenza virus. Administration of well tolerated doses of rIL-2 before inoculation of antigen or infectious agent is not likely to be harmful and may even enhance protective immunological responses.