Bronchial reactivity in relation to immune responses in rats after subcutaneous sensitization without adjuvant

Rats of BNxWi /Fu strain were immunized by daily subcutaneous (s.c.) injections of antigen without the use of adjuvant for two 2-week periods with a 4-week interval. The bronchial responses to airway and intravenous (i.v.) antigen challenge were measured during and after the immunization period. These responses were compared with both the humoral and the cell-mediated immune response of the animals. Immunization induced bronchial reactivity of the animals to antigen after airway and i.v. challenge. This reactivity persisted for 7 weeks following the second immunization period. Specific IgE antibodies were detected in serum, bronchial fluid and in supernatants from cultured peripheral lymph node cells. The immunization also resulted in an IgG antibody response. Neither the amount of IgE, IgG2a, nor of any other isotype, correlated with the bronchial reactivity in the animals. Antigen stimulation of lymph node cells mixed with syngeneic spleen cells induced proliferation. This procedure also resulted in a maturation of mast cells in 3-week cultures. The immunization also resulted in some increase in the number of mast cells around vessels in the lung. There was no correlation between these parameters of cell-mediated immunity and either antibody responses or bronchial reactivity.