What’s the practical difference between T-cell memory and B-cells (antibodies)? Are they equally good at providing immunity?
In: Biology
One isn’t necessarily better than the other. T and B cells do completely different things, and the best protection you can get is going to involve both.
As for the practical differences:
– B cells, during an immune response, differentiate mostly into plasma cells which are focused on pumping out as much high-affinity antibodies as possible (they have a very interesting evolution-like mechanism going on by which they fine-tune and optimize their antibody by a factor of around 10,000, given a few days). Most of them die afterwards, but some become memory B cells, which essentially means that this highly optimized antibody is preserved for future use. In addition to having a powerful antibody from the get go, they also require less confirmation from other parts of the immune system before cranking up production if the relevant pathogen is encountered again, so the antibody response happens much faster overall.
– T cells come in two main flavors, helper and cytotoxic. Helper T cells mediate information between other parts of the immune system (including the confirmation for B cells described above), and can provide a great variety of chemical signals to put surrounding cells, even those not normally part of the immune system, in a state of alert. They don’t really provide any direct sort of pathogen killing mechanisms by themselves, but are absolutely critical to adaptive immunity overall (the extreme state of immunocompromise seen in untreated HIV/AIDS patients results from these guys dying off, just to give an example of how important they are). Like B cells, most of them die after an infection resolves, but some survive as one of several different memory T cell types.
– Cytotoxic T cells are focused on killing cells, particularly your own. This is most important in the context of viruses and intracellular bacteria, which evade other parts of the immune system by hiding in the host’s own cells. They also play a major role against cancer. If a cytotoxic T cell detects anomalies about what a cell is doing (every cell reports what’s going on inside, and if they don’t, another type of immune cell will kill them), it will force a cell to self-destruct. Again, some of these survive as memory after an immune response is over.
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