It is said "No T cells, no immunity." Explain this statement?

Answer 1

T cells are lymphocytes that mature in the thymus (hence T).They form an important part of your 'adaptive' immune system transported in the blood, along with other cells. T cells have special antigen receptors on their surfaces and can bind to a specific shape, then multiply themselves so they form an 'army' of specialised fighting cells. They fight things such as pathogenic bacteria as well as viruses, parasites, fungal spores and all manner of things that could make you ill.

There are different types of T cells that work in different ways e.g. cytotoxic T cells and Helper T cells which are specialised to fight infection etc. With repeated infections, they become more efficient producing various substances that can e.g. kill viruses. They work in conjunction with the B cells, another type of lymphocyte which produce antibodies to the marauding bacteria etc.

So without T cells, you would be left with generalised or innate immunity (non-adaptive) which would help fight infection to some extent (e.g. by phagocytosis i.e. gobbling up bacteria etc), but would not 'remember' infections next time around like the more effective 'adaptive' immune system.

Answer 2

A point that one of the responders was on track to making was about B-Cells. Antibodies are the first line in adaptive immunity. In order for you to make proper antibodies for a given antigen, T-Cells must interact with B-cells, inducing the B-cells to undergo isotype switching. This means converting B-cells from cells that produce IgM antibodies, to B-cells that produce more usable forms (predominantly IgG). This is also important for memory, where these activated B-cells can become plasma cells (cells that will immediately produce the specific antibody) and memory cells (cells that can in the future upon antigen exposure proliferate and produce specific antibody).

This is the concept of immunization/vaccination. The ability to produce antibody quickly and in high amounts when an antigen is encountered. And the production of this antibody is TOTALLY dependent on T-cells.

Answer 3

T Cells are those blood cells which fight infection and stop you from becoming ill - during cancer treatment or AIDS these cells can be damaged or killed off, thus a simple cold could kill you as you have no t cells with which to fight it off, and therefore no longer have any built in recovery service in your immune system - no immunity.

Answer 4

T-cells help in recognising that something is wrong inside the body, when you've been infected with something. If your T-cells don't recognise something is wrong, or that something is there that shouldn't be, there is nothing to stop the foreign body from killing you. Which is why HIV, which targets T-cells, is so deadly. No T-cells, no immunity.