Augmented production of colony-stimulating factor in C3H/HeN mice immunized with Nocardia rubra cell wall skeleton

C3H/HeN mice subcutaneously injected repeatedly with Nocardia rubra cell wall skeleton (N-CWS) acquired cellular immunity against N-CWS. In these N-CWS-immunized mice, the serum colony-stimulating factor (CSF) and granulocyte-macrophage colony-forming units in the bone marrow remarkably increased after an intraperitoneal (i.p.) injection of N-CWS compared with those in normal control mice given an single i.p. injection. To analyze the effects of secondary immune response to N-CWS on CSF production by splenocytes, whole mononuclear leukocytes (WMNL), nylon fiber-nonadherent splenocytes (NADC), and plastic-adherent splenocytes (ADC) were cultured in the presence of N-CWS, and then the supernatants of each cell fraction were assayed for CSF. A fraction of WMNL from immunized mice was found to produce more CSF than WMNL from control mice, and either fraction of NADC or ADC separated from WMNL produced markedly less potent CSF when cultured separately. However, when NADC from immunized mice were cultured with ADC from either immunized or normal mice, CSF production recovered to the level shown by WMNL. The role of ADC could be substituted for by cell-free culture medium of either ADC plus N-CWS or the J774 cell line, in which high interleukin-1 activity was detected. A surface marker study showed that depletion of either Lyt-1.1+ or Lyt-2.1+ cells caused a striking loss of CSF production. These data suggested that CSF in the sera of immunized mice challenged with an N-CWS i.p. injection is mainly produced by N-CWS-sensitized T lymphocytes with help of a macrophage-derived humoral factor(s).