CD8A and infection: By 7 days following infection the mean proportion of CD8 T cells that were CD45.2 (IL-18Rα-/-) was 53% with a range of 38-63% in the experimental chimeras, and in the control chimeras the fraction of CD8 T cells that were CD45.2 (IL-18Rα+/+) was 39% with a range of 31-46%.