Local and systemic cellular immune responses in guinea-pigs given antigen parenterally or directly into the lower respiratory tract.

Guinea-pigs were immunized with DNP-HGG either by direct injection into the lower respiratory tract or intravenously. The distribution of cellular sensitivity was assessed by means of the macrophage migration inhibition test applied to bronchial wash cells (local) and to peritoneal exudate and spleen cell suspensions (systemic). A single low antigen dose given locally via the intratracheal route was sufficient for stimulation of cellular immunity in bronchial wash cells and oil induced peritoneal exudate cells but not in cells obtained from the spleen. Alternatively, a low antigen dose given intravenously resulted in splenic and peritoneal exudate cell sensitivity but not by cells obtained from the bronchus. Under these latter conditions, however, the bronchial wash cell population could be rendered sensitive to the systemic antigen providing sensitization was accompanied by a non-specific local stimulation—such as injection of a non-cross-reacting protein. Although a local low antigen dose does not normally result in systemic cellular immunity as judged by spleen cell assays, cellular sensitivity was induced systemic-ally by increasing the amount of locally administered antigen given as a single injection or increasing the number of low dose injections. Furthermore, under conditions of multiple injection, the onset of a measurable response at any site was accelerated. Experiments to determine the fate of locally injected antigen revealed that proteins do escape from the lung into the general circulation as intact molecules. In addition to other parameters affecting the distribution of cellular immunity, the implication of these findings with special regard to respiratory tract prophylaxis are discussed.