Explain how HIV targets T helper cells, why TB becomes severe, how infection causes disease and how treatment changes survival and case numbers.
Mycobacterium tuberculosis (Mtb) and human immunodeficiency virus (HIV) are two pathogens that infect people. When people infected with either pathogen become infected with the other pathogen the disease is worse.
Explain why HIV infection causes tuberculosis (TB) to be worse.
An explanation that includes four of the following points:
- HIV's host cell is T helper cells / HIV \{targets / infects \} T helper cells (1)
- number of T (helper) cells reduced / T (helper) cells \{destroyed / killed\} (by HIV) (1)
- when HIV enters lytic \{cycle / phase\} (T helper cells are destroyed) (1)
- without T helper cells the (humoral) immune response is \{not initiated\} / weaker\} (1)
- therefore Mtb are not opsonised (1)
- and therefore without antibody phagocytosis (of M t b ) is not so effective (1)
ACCEPT CD4 cells attacks DO NOT ACCEPT other named cells
ACCEPT \{replication / reproduction\} stage comes out of latency
ACCEPT B cells not activated person is immunocompromised IGNORE T killer cells not activated
ACCEPT no antibodies to bind to Mtb agglutination (TB) bacteria
ACCEPT description involving macrophages providing ref to lack of antibodies