Certain thymus-independent antigens called TI-1 antigens have an intrinsic capacity for inducing immature B cells as well as mature B cells to proliferate. They bind to receptors on B cells whose stimulation induces proliferation and differentiation. The concentration of antigens required to induce activation is much higher than normally encountered. Antigens that can cause such polyclonal activation are known as B-cell mitogens, because they drive B cells into DNA replication, mitosis and cell division. An example is the lipopolysaccharides (LPS) of gram negative bacteria.
In an infection, the lower mitogenic stimulus will activate B cells only in combination with signalling through the B cell receptor. Without the participation of T cells, no cytokines are produced, only IgM antibodies. There is no long-lived immunity (“memory”) and no response can be produced in infants less than 2 years of age. However, with the advent of conjugated vaccines which bind a polysaccharide to a toxoid, memory has been induced in some cases.
(Text taken from “the immune system”, Parham, Garland Publishing 2000 page 163.)
Which of the following antibodies is rapidly produced and but can not provide long-term memory:
Extra info: IgG is also rapidly produced, and confers long-term memory.