Overview
How HIV Weakens Host Defence
HIV infects CD4+ T lymphocytes, cells that coordinate much of the adaptive immune response.
HIV infects CD4+ T-lymphocytes, cells that coordinate much of the adaptive immune response. CD4 cells help organize communication between immune cells, support antibody production, and direct responses against intracellular pathogens. As HIV replicates, the CD4 count progressively falls and the immune system loses the ability to mount coordinated protection. A low CD4 count is not simply a laboratory abnormality. It predicts what infections the body may no longer contain. A count below 200 cells/µL indicates severe immune suppression and a markedly increased risk of opportunistic infection. Organisms that would usually cause little illness can then produce severe pneumonia, persistent mucosal infection, disseminated disease, or neurological illness. HIV may cause few symptoms for a long time, but absence of symptoms does not mean absence of viral replication. HIV-1 RNA viral load measures circulating virus and is used to assess response to therapy. The CD4 count describes immune reserve. Both matter: viral load shows how successfully treatment is suppressing HIV, while CD4 count helps identify vulnerability to immune-related complications.