INTRODUCTION - ACQUIRED IMMUNITY
Acquired immunity results in the formation of antibodies.
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SCENARIO
You get an infectious disease, and you survive it. You produce antibodies You do not get that infectious disease again. You have become immune to it because you are exempt from the disease. In other words, by coming into contact with the infectious organism, you acquire immunity to it (assuming that your immune system is working properly) |
The acquired immune system consists of lymphocytes.
Like other blood cells, lymphocytes originate in the bone marrow as stem cells.
At a later stage, they mature into:
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T-cells |
or
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B-cells. |
T-cells are called T-cells because they mature and differentiate into their various roles in the Thymus (which begins with a 'T').
B-cells, on the other hand, mature in the bone marrow (which begins with a 'B', hence they are called B-cells).
The Thymus:
The thymus gland is an organ that is situated behind and just below the sternum.
It is quite large in babies and young children, but it atrophies (shrinks) as we get older, so that by the time you reach my great age, it has almost disappeared.
In the thymus, the immature T-cells learn to differentiate between cells that belong to us, and cells (and pathogenic micro-organisms) the are 'non-self' or 'foreign'.
In addition, it is in the thymus that the T-cells differentiate into different subsets.
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You will learn more about this in the section on T-cell (or cell-mediated) immunity. |
As you have already found out above, B-cells mature in the bone marrow.
When activated by an infectious micro-organism, many of the B-cells change into plasma cells.
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Again, you will learn more about this in the section on B-cell (or humoral) immunity. |