The second type of thymus-independent antigens, called TI-2 antigens, activate only mature B cells. TI-2 antigens are typically composed of repetitive carbohydrate or protein epitopes present at high density on the surface of a microorganism. Typical antigens of this kind are bacterial cell wall polysaccharides. It is thought that they cross-link the B cell receptors and co-receptors to such an extent that the need for additional signals is overridden. Human B cells develop
Text taken from “the immune system”, Parham, Garland Publishing 2000page 163.
Pneumococcal vaccines need to be given:
Extra info: Close The pneumococcal vaccine is given yearly based on two factors. 1) the vaccine does not confer long-term immunity and 2) the composition of the serotypes changed each year depending on risk.