Immunology

Interleukin 1 in Oviductal Tissues of Viviparous, Oviparous, and Ovuliparous Species of Amphibians

Abstract
In previous reports, we showed that Interleukin 1 (IL1), a cytokine associated with implantation in mice, is also expressed in reproductive tissues of viviparous squamate reptiles and cartilaginous fishes. Here, we investigated expression of IL1B and its functional membrane receptor type I (IL1R1) in amphibians, a class of vertebrates characterized by different reproductive modes including internal and external fertilization. In particular we investigated the oviductal tissues of the aplacental viviparous Salamandra lanzai, the oviparous Triturus carnifex and the ovuliparous Bufo bufo. By immunohistochemistry using anti-human IL1B and IL1R1 polyclonal antibodies we demonstrated that in S. lanzai, most cells in the uterine mucosa were immunoreactive for IL1B and IL1R1. In T. carnifex, IL1B and IL1R1 were present in ciliated luminal cells, and there was evidence of IL1B in glandular cells. In B. bufo, expression of IL1B and IL1R1 was limited to the apical cytoplasm of the ciliated oviductal cells. Western blot analysis showed that a putative mature form of IL1B, similar to that in mammals, was present in oviductal tissues of S. lanzai whereas different forms, likely corresponding to an inactive pro-IL1B protein, were found in T. carnifex and B. bufo. A band corresponding to the predicted 80 kDa human IL1R1 was found in S. lanzai and T. carnifex. Although this study showed that IL1B and IL1R1 expression occurred in all reproductive modes, the differential expression from ovuliparity to oviparity and viviparity may reflect the different roles of IL1 system in the various reproductive modes.

Key words: Female Reproductive Tract • Immunology • Cytokines • Fertilization • Oviduct