1Biochemistry Department, Faculty of Science, Ain Shams University; Allergy and Immunology Division, School of Medicine, University of Pennsylvania, Philadelphia, USA and Microbiology Department, Faculty of Medicine for Girls, Al Azhar University, Cairo, Egypt.

We have previously demonstrated that vaccination of mice with ultra-violet (uv) attenuated cercariae of Schistosoma mansoni induces significant level of cell mediated immunity. Other in vivo and in vitro studies in similar vaccine models have demonstrated the predominance of the T helper-I (Th1) cytokine responses mainly interferon-gamma (IFN-g) in pulmonary immune mechanisms. The current study extends this analysis to include Th2 responses and compares the kinetics of pulmonary cytokine production during the time period that coincide with schistosome migration in the lung with that of the systemic production by spleen cells. An ELISPOT assay was used to identify and enumerate lymphocytes that produce IFN-g and interleukin-4 (IL-4). Following the second vaccination dose, the number of pulmonary leukocytes capable of producing IL-4 and IFN-g increased significantly. The maximum number for IL-4 secreting cells was 32 cells/106 at day 6 (p<0.05) while that for IFN-g was 33 cells/106 at day 14 (p<0.05) as compared to 8 cells/106 and 2.8 cells/106 for naïve animal respectively. in contrast, IL-2 was not detected at any time period. Splenocytes also demonstrated increase in the number of cells producing IL-4 reaching up to 7 folds at day 10, IFN-g 12 folds at day 14, and IL-2 15 folds at day 10 (p<0.001). Following challenge infection, significant increase in IL-4 was demonstrated in lung at day 14 (p<0.001) and spleen at day 10 and 14 (p<0.05), while IFN-g in spleen was 2 folds at day 21 (p<0.05). It is concluded that in the uv-attenuated cercariae model the lung is a major site for IFN-g production post vaccination while IL-4 is the predominant cytokine after challenge with normal parasites.