203 SummaryIn conventional mice colonies, mouse pinworm, Syphacia obvelata is found very often. Several studies indicate that infection with this parasite can modulate the immune system of the host and can affect experimental final results. The aim of our study was to investigate the most immunogenic proteins of S. obvelata inducing both local and systemic immune response in naturally infected laboratory mice. Protein extracts of S. obvelata were analysed by Western blotting to examine their antigenic character. The antigens were probed with serum and mucosa of S. obvelata naturally infected mice. Surface and somatic antigens were recognized by serum and mucosal IgG, IgA and IgM antibodies. The most immunogenic and dominant proteins were observed. Proteins of Mw ~ 70, 65 and 48 kDa showed the most evident reaction with serum and mucosa antibodies of infected animals. Surface and somatic antigens of nematode S. obvelata eliciting immune response in laboratory mice may be useful in development of a diagnostic test which could be applied for the infection control prior the experiments.