CD8+ T lymphocytes are not required for murine resistance to human filarial parasites

Mice are resistant to the establishment of infection with the nematode parasite Brugia malayi, an etiologic agent of human lymphatic filariasis. We have recently shown that T and B lymphocyte-deficient C.B.-17 scid/scid mice are permissive for infection with this parasite, whereas coisogenic C.B.-17+/+ mice are resistant. This observation suggests that T and B lymphocytes that comprise the antigen-specific immune system orchestrate murine resistance to B. malayi. In order to define the component of the antigen-specific immune response that is responsible for this resistance, we have tested the susceptibility of beta 2M-/- mice to infection with B. malayi L3 larvae. These mice are homozygous for insertional disruption of their B2m genes, which encode beta 2-microglobulin, the small subunit of the major histocompatibility (MHC) antigens. They do not express beta 2-microglobulin and, as a consequence, fail to express the class I major histocompatibility antigens, and they do not develop the CD8+ class I MHC-restricted cytotoxic T cell subset. We find that these mice are completely resistant to B. malayi, indicating that the CD8+ T lymphocyte subset is not an obligate requirement for murine resistance to human filarial parasites.