CD4 counts are also used to decide on prophylaxis against opportunistic infections, for instance to screen for cryptococcal infection in patients with ≤ 100 CD4 cells/μL and stop prophylaxis when patient presents with > 200 cells/μL, or start co-trimoxazole in case CD4 counts are ≤ 350 cells/μL [3]. Here, CD4 is linked to Opportunistic infection.