CD8A and viral infectious disease: CD8 lymphocytes in SLE patients are characterized by reduced response to viral infections, and this has been attributed to the reduction of Signaling lymphocytic activation molecule family member 4 (SLAMF4) expressed on memory CD8+ cells, increased expression of PD-1 CD8 cells, and transformation of CD8+ to Double-Negative T cells (DN T cells) [243,244].