Structural differences between a B cell and a plasma cell in relation to their function?

Which cell actively produces antibodies during an immune response? B lymphocyte T lymphocyte plasma cell

An infant appears healthy until about 9 months of age, when he develops severe bacterial infections, one after another. Fortunately, theinfections are treated successfully with antibiotics. When infectedwith the measles and other viral diseases, the infant recovers withoutunusual difficulty. Explain the different immune responses to theseinfections. Why did it take so long for this disorder to become apparent? (Hint: Consider IgG.)

Explain how two major types of lymphocytes are formed and activated, and how they function in immune mechanisms.