Additionally, adoptive transfer of CD4+ T cells from resistant BALB/c mice into severe combined immunodeficiency (SCID) mice, which lack the adaptive arm of the immune system and therefore are susceptible to infection, resulted in worm expulsion proving that CD4+ T cells, and not CD8+ T cells or B cells, are crucial for the development of protective immunity to T. muris [23]. Here, CD8A is linked to infection.