IL-4 was first described in 1982 as a
cofactor in the proliferation of resting stimulated through the
cross-linkage of their membrane
by anti-IgM . It was also described as a
factor that induced B-cell differentiation into plasma cells
secreting . Hence its early names were B-cell stimulation
factor-I (BSF-I), B-cell differentiation factor-I (BCDF-I) and B-cell growth factor-I (BCGF-I).
different effects on at different stages in the cell cycle. On resting B-cells,
IL-4 acts as an activating factor, inducing them to enlarge in size and increase class II
Following activation by an or mitogen, IL-4 acts as a growth factor, driving DNA replication in the
B-cells. In the case of proliferating B cells, IL-4 acts as a differentiation factor by regulating
to Cepsilon and Cgamma1, i.e.,
the production of the and IgG1 subclasses.
In this role it has been termed a "switch-inducing" factor.
IL-4 also plays a major role in T-cell development. It is thought to be influential in promoting
differentiation of T helper cells into during an immune response.
IL-4 can also act as a
IL4 actions (except increases in MHC II) are "neutralized" by
, which is made by .