What is the difference between the primary and secondary immune responses? (May be asked in the form of how to interpret a commonly used graph on the subject)

In a primary immune response the active immune system must first recognise the pathogen via B-lymphocyte cells with antibodies on their surface that are complementary to the antigens of the invading pathogen (clonal selection), this can occur via an antigen directly binding to the B-lymphocyte receptor or a T-lymphocyte activating it. Once this occurs the B-lymphocyte divides (clonal expansion) and then differentiates into a plasma cell that produces antibodies at a high rate. This process takes a few days.
In a secondary immune response (reinfection) many complementary B-memory cells left over from the primary response are already in the bloodstream and rapidly recognise the pathogen. They divide and differentiate into plasma cells that produce antibodies at a rapid rate quickly killing the pathogen. Thus, the end result is that pathogen levels decrease faster in the secondary immune response and antibody levels rise faster and higher (explain this via drawing out a graph).

Related Biology A Level answers

All answers ▸

Describe how mRNA is produced in the nucleus of a cell


Name the process by which fatty acids and glycerol enter the intestinal epithelial cell from the lumen of the intestine


What is the electron acceptor used in photosynthesis


What is oxidative phosphorylation?