SYSTEMIC AND PULMONARY IMMUNE-RESPONSE TO INTRABRONCHIAL ADMINISTRATION OF OVALBUMIN IN CALVES

Local immunization of the respiratory tract may be the best way to ach ieve protection against respiratory pathogens, In order to do so succe ssfully, it is important to fully understand how the immune response t o antigen administered via the respiratory route develops. We studied the respiratory and systemic immune response after subcutaneous (SC) a nd intrabronchial (IB) inoculation of calves with ovalbumin (OVA). Eig ht calves received two SC inoculations of OVA and eight other calves r eceived two SC and three additional IB inoculations of OVA. The occurr ence of OVA-specific antibodies and antibody-secreting cells (ASC) was measured over time using isotype-specific enzyme linked immunosorbent assay (ELISA) and ELISPOT. SC immunization of calves did not result i n OVA-specific IgA in bronchoalveolar lavage (BAL) fluid, Subcutaneous priming followed by intrabronchial challenge caused an initial IgG1 r esponse in the bronchoalveolar lavage fluid, followed by a large IgA r esponse. The presence of IgG1-ASCs indicated that the IgG1 was at leas t partially locally produced. Most of the OVA-specific IgA in the BAL fluid was secreted by pulmonary ASCs as indicated by the large number of IgA-ASCs in BAL samples and the low serum level of OVA-specific IgA . Antigen-specific IgG1 ASCs were detectable among peripheral blood mo nonuclear cells after culture with OVA.