The
complement system, which plays an important role in inmate immunity, is considered to be important in the pathophysiology of allergic
asthma. A patient with allergic
asthma shows the reversible characteristic system of bronchoconstriction, increased mucus secretion, and complicated airway
inflammation. Various
cytokines secreted from Th2 cells contribute to the system. Cysteinyl-
leukotrienes (CysLTs) are also considered to be one of the important mediators involved in asthmatic pathophysiology. However, the effects of a
drug on humans may not be the same as those on animals due to species differences in
complement-related molecules. In this series of experiments, we tried to establish a model in which the effects of a
drug on the production of CysLTs from human lung preparations were evaluated following an
anaphylactic reaction. CysLT production increased when the passively sensitized lung tissues were stimulated with
anti-IgE antibody. The coaddition of
anaphylatoxin, C5a, with the
anti-IgE antibody potentiated CysLT production. The response to C3a was weaker when compared with that to C5a. In addition, increased production of CysLTs by adding serum at a specific ratio was dose dependently inhibited by nonpeptide
C5a receptor antagonist,
W-54011, or a novel complementary
peptide inhibitor of C5a, acetyl
peptide A. From these results, it is suggested that C5a potentiates cysLT production from human lung tissues and contributes to allergic
inflammation like
asthma, and thus
acetylated peptide A and
W-54011 are useful for suppressing allergic
inflammation in the lungs.