To investigate cytokine production stimulated by diesel exhaust particulates (DEP) and antigen through the intranasal route, mice were administered with DEP mixed with ovalbumin (OA) 3 times at an interval of 3 weeks. After the last instillation, cervical lymph node cells (LNC) were cultured in vitro with OA and antigen-presenting cells. The proliferative response to OA in cervical LNC from mice instilled with DEP and OA was noted to have increased significantly compared to mice instilled with OA alone. Interleukin 4 (IL-4) and interferon (IFN)-gamma in culture supernatants were measured with ELISA. OA-stimulated IL-4 production in cervical LNC from mice instilled with DEP and OA markedly increased beyond that in the control mice. In contrast, OA-stimulated IFN-gamma production in cervical LNC from mice instilled with OA was 3 times that for DEP and OA-instilled mice. OA-specific IgE antibody in sera showed a trend to be increased in mice intranasally instilled with DEP and OA. These results suggest that intranasal instillation of DEP and antigen in mice may modulate in vitro antigen-stimulated cytokine production from cervical LNC with a consequent increase in IgE antibody production.