Antigens which trigger specific T cells are called T-d__t antigens. In the absence
of T cells, these antigens cannot t___r B cells to synthesize antibodies. T-
independent antigens, on the other hand, can stimulate _ cells without the aid of _
Most antigens are _-dependent. They include m____sms, proteins, and h___ns
on various carriers. T-dependent antigens react either directly with a T cell, or with
a macro___e which processes the information and transfers it to a T cell. T cells
that function in this mechanism are called h___r T cells. These antigens may
induce IgG, IgE, IgA, or IgM responses and produce immunological m____y.
T-independent antigens are generally large polymers with many r__g units. It
appears that each T-independent antigen carries a specific a___c signal and a
nonspecific s__nal which acts as a mitogen. (A mitogen is a substance that
induces m__s or cell tr____tion, particularly transformation of lymphocytes.) This
mitogenic signal is directly capable of a____ting B cells irrespective of their
Although T-independent antigens can initiate antibody production in the absence
of T cells, substantial production of antibody (does) ( does not) occur. The
antibody produced is largely IgM and little or no immunological m_____y is
Early evidence about hapten-carrier systems suggests that T cells recognize the
c___r while B cells recognize the h___n. As discussed previously, h__s alone are
not able to induce immune responses. If the hapten is coupled to a c____r,
antibody that reacts with the h___n will be produced. The B cell which binds the
hapten will make antihapten a_____y.
Once B cells are stimulated, they become metabolically active and undergo
m_____cal changes. This process is called blast ___ion. B lymphocytes are
small oval cells, but after transformation they become en____d. B cells then go
through several cell divisions called c__nal expansion in order to increase the
number of activated cells. They then differentiate into p__a cells and m__y B
cells. Plasma cells secrete a____s. They are e___d cells and survive only about
two w___s. Memory cells have the same appearance as small l___cytes.
Memory cells are responsible for the a___tic response, the rapid production of
antibody on re-e___re to antigen.