Immunotherapy for Infectious Diseases

Humoral Immunity 5
Fig. 1. Humoral and cell-mediated responses of antibodies to antigens. CTL, cytotoxic
T-lymphocyte.
secreted by plasma cells, which are found mainly within lymph nodes and which do
not circulate. Plasma cells are derived from B-lymphocytes (Fig. 3).
As seen in Fig. 2, the immunoglobulin molecule consists of two light chains,
each of approximate molecular weight 25,000, and two heavy chains, each of approximate
molecular weight 50,000. IgA exists in monomeric and dimeric forms and IgM
in a pentameric form of 900,000 kD. The links between monomers are made by a
J chain.
Additionally, IgA molecules receive a secretory component from the epithelial
cells into which they pass. This is used to transport them through the cell and
remains attached to the IgA molecule within secretions at the mucosal surface. The
heavy and light chains consist of amino acid sequences. In the regions concerned with