The Immune System

The immune system is vastly complex but unfortunately my notes are rather limited. If you wish to learn more about the immune system you'll have to find your own resources for now until I take a microbiology and immunology in 2nd year and can share what I learn with you :P

1. How do natural killer cells differ from T-cells in their recognition of an enemy?

While natural killer cells and T-cells kill off invaders through a similar mechanism (contact followed by release of certain enzymes), they differ in their recognition of an enemy. T-cells have T-cell receptors that recognise particular antigens on the surface of invading cells and are thus relatively specific. Natural killer cells, on the other hand, simply look for whether or not an invader has a "self" marker on the cell surface, and can thus kill a wide variety of invaders. These markers are called major histocompatibility (MHC) antigens, and differ from person to person (except in the case of identical twins).

2. What cells are affected by HIV virus? What is the difference between HIV infection and AIDS?

HIV (Human Immunodeficiency Virus) affects CD4+ cells by entering and multiplying rapidly, destroying the cells in the process. Some of these CD4+ cells are CD4+ lymphocytes, which fight against infection. Hence, HIV weakens the immune system. This condition can lead to AIDS (Acquired Immune Deficiency Syndrome), in which the immune system is too weak to fight off regular infections, leading to otherwise harmless infections to become deadly.