1

If we have a B cell for every possible type of antigen, why aren't all of them memory B cells? From my reading, I have deduced that memory B cells are effectively the better version of normal B cells, activating faster and being more effective, which is why pathogens that are exposed again are typically dealt with much quicker. But why go through the trouble of getting infected, only to have to gain "immunity" to easily defeat the threat the second time. If all B cells are memory cells, the thought of autoimmune diseases and allergies being extremely common may arise. However, our own B cells have mechanisms that prevent them to attack self and allergies. I know that this could just be a product of evolution, but I wonder if there is a clear reason of why this wouldn't work.

(please note that I have no other experience of the immune system besides reading books, watching videos, and google searches, so feel free to point out possible misconceptions I may have [also this is my first post so hopefully I am clear with my question!])

Avkash Panwar
  • 11
  • 1

1 Answers1

0

When the naïve B-cell is produced, the body does not automatically "gain immunity" to a certain infection. There is only a certain amount of B-cells with a certain antibody for a specific antigen, and it is not enough to create an immune response on its own. When the antigen binds to the antibody and activates the B-cell, more of that B-cell is made, creating a secondary clonal selection process. This process is what kicks of the immune response. Some of the B-cells become plasma cells (the cell that produces large quantities of antibodies) and others become memory B-cells. The memory B-cells exist in greater quantities than the naïve B-cells, which means that the response will be better due to the greater number of cells present. The memory B-cells are also created to be more responsive than naïve B-cells when exposed to the antigen, which speeds up the process and leads to a better immune response the second time around.

In short, the reason why all B-cells aren't memory cells is because there are different types of B-cells that do something different: naïve B-cells are the "parent" to all of the other types of B-cells which have to be activated to create other cell types, plasma cells produce antibodies, and the memory B-cells are cells that have improved upon the naïve B-cell to create a faster response. This is why the body needs to be infected once for the secondary immune response to be fast, the body needs to have that secondary B-cell selection that picks the right B-cell for the right antigen.

Source for Information: Prescott's Microbiology 12th Edition by Willey, Sandman, and Wood

RoyGenesis
  • 51
  • 6
  • Thanks for the response! However, why do naïve B cells have a slower response anyways? What's the point of created memory B cells that are faster when the naïve ones can be faster anyways? I mean evolution doesn't have a "point", but it would be a lot more efficient for naïve B cells to respond fast the in the first place. – Avkash Panwar Feb 01 '24 at 23:40
  • I mentioned this in an answer for a different question (link), but evolution goes for survival of the fittest, not for efficiency. If it is good enough to survive, it doesn't need to evolve further. I hope that helps! – RoyGenesis Feb 04 '24 at 01:51