When learning about the immune response, my teacher mentioned that all the bodies B cells are present at birth, and there is one to counter every disease. But if this is the case, why should the primary response take a long time?
As far as I know, the primary response involves the non-specific response followed by the specific response, where APCs cause the activation of T cells resulting in clonal selection and expansion of T and B cells. The B cells then differentiate into plasma cells and produce antibodies. It results in the memory cells being produced, which can quickly reengage the specific response the next time the pathogen enters.
Why doesn't the body just make memory cells to begin with? As if it has already encountered every possible pathogen. I presume it is just a lack of specificity in the A level teaching, but I am curious to know what I am missing here.