The answer is skin
The first line of defence is your innate immune system. Level one of this system consists of physical barriers like your skin and the mucosal lining in your respiratory tract. The tears, sweat, saliva and mucous produced by the skin and mucosal lining are part of that physical barrier, too.
Answer:
HIV may affect erythropoiesis directly through infection of red cell precursors and bone marrow stromal cells.
