Tehran University of Medical Sciences Iranian Journal of Public Health 2251-6085 36 4 2007 12 15 87 90 AH Keyhani MR Nowroozi 2015 10 03 Background: The serum levels of C3, C4, and the total hemolytic activity of complement system (CH50) of patients ex­posed to mustard gas (MG) in the battlefield were measured in this study. Methods: C3 and C4 were measured by single radial immunodifusion and CH50 was evaluated according to total hemolytic activ­ity of the serum. Results:  The serum levels of C3 showed a significant increase on day 3 after exposure to MG. The serum levels of C3 in the sera of patients collected during 4-18 and 19-31 days after exposure to MG were also found to have increased significantly com­paring to those of the controls. The levels of C4 in the sera of patients collected from the patients during 4-18 and 19-31 days after exposure were also found to be significantly higher than those of the controls. However the increase in the serum lev­els of C4 were not in the same magnitude as those of the C3. The serum CH50, which is a measure of the total hemolytic activ­ity of classical complement system also showed a significant increase in patients' sera on day 3 and in the sera collected dur­ing 4-18 days after exposure. However, the CH50 in the sera of patients showed a decrease in the sera collected during 19-31 days after exposure to MG. Conclusion: Since C3 is an acute phase protein as well as a complement component, these results are discussed in terms of a vigorous acute phase response and activation of the complement system. https://ijph.tums.ac.ir/index.php/ijph/article/view/2096 https://ijph.tums.ac.ir/index.php/ijph/article/download/2096/2077