Note: this site last updated in 2006
The human immune system
An article from "The Molecules of HIV" (c) Dan Stowell
The mammalian immune system is a fantastic, and fantastically-complex, system. There are a number of cells specialised for particular jobs in recognising and defending against foreign materials that might enter the body (e.g. bacteria or viruses). Some of these cells also play roles in other procedures such as wound-healing. There are differences in the immune systems of different species - humans, primates, etc. - and since we're interested in HIV, we'll just look at the human immune system for now.
The following image shows a summary of the important cells and molecules in the human immune system - the top half of the picture represents detection of invaders, and the bottom half represents the defence which is triggered by that detection.
From our perspective of HIV, the most important cells are perhaps the lymphocytes - indeed, one specific type, called "T lymphocytes" or "T cells". They are the cells which HIV targets and infects. In ordinary immune function, T cells often work together with the other major type of lymphocyte: B lymphocytes or B cells. Notice the position of the helper T cells in the diagram (labelled TH) - they're in the middle, the key in the transition from detecting an invader to launching a defence against it.
Also important are macrophages, cells which effectively "eat" invaders. HIV does target macrophages, but to a much lesser extent than T cells.
Antibodies (immunoglobulins) aren't cells, but are molecules secreted by the immune system - molecules designed to latch on to invaders and to neutralise them in various ways, and also to trigger certain activities of the immune cells. You can see some of them indicated in the diagram, including various interleukins (labelled IL). Cytokines too are important molecules in the immune system - they are molecular signals emitted by lymphocytes and other cells.