Unknown functions of immunoglobulins A.
Traditionally, the function of immunoglobulins A (IgA), the major type of secreted antibodies, has been thought to be restricted to binding antigens outside the epithelium basal membrane. Therefore, effector mechanisms eliminating IgA-opsonized targets have not been investigated so far. However, some indirect observations of infectious agents penetrating into tissues and blood from the environment suggest such mechanisms (analogous to IgG/IgM-dependent activation of complement and natural killers). In the present review, we examine details of IgA structure that might contribute to elucidation of IgA-dependent effector functions in human and animal immunity. Special attention is given to a putative transduction of signal about antigen binding in the active center of IgA from the Fab- to the Fc-superdomain via intramolecular conformational rearrangements. Different structure of the IgA subclasses (IgA1 and IgA2) is examined taking into account probable divergence of their functions in immune response.
Kazeeva
T N
TN
Bach Institute of Biochemistry, Russian Academy of Sciences, Moscow 119071, Russia.
Shevelev
A B
AB
D000595:Amino Acid Sequence; D000818:Animals; D006801:Humans; D007109:Immunity / Q000276:immunology*; D007070:Immunoglobulin A / Q000737:chemistry / Q000235:genetics / Q000276:immunology*; D008958:Models, Molecular; D008969:Molecular Sequence Data; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction / Q000276:immunology*
D007070:Immunoglobulin A