Rather, the significant biological effects are a consequence of secondary "effector functions" of antibodies.The immunoglobulins mediate a variety of these effector functions.Each Fab fragment is monovalent whereas the original molecule was divalent.
Usually the ability to carry out a particular effector function requires that the antibody bind to its antigen.
Not every immunoglobulin will mediate all effector functions. Fixation of complement - This results in lysis of cells and release of biologically active molecules (see chapter two) 2.
The F(ab')2 binds antigen but it does not mediate the effector functions of antibodies. Immunoglobulin classes The immunoglobulins can be divided into five different classes, based on differences in the amino acid sequences in the constant region of the heavy chains.
All immunoglobulins within a given class will have very similar heavy chain constant regions.
When the amino acid sequences of many different heavy chains and light chains were compared, it became clear that both the heavy and light chain could be divided into two regions based on variability in the amino acid sequences. Light Chain - VL (110 amino acids) and CL (110 amino acids) 2.
Heavy Chain - VH (110 amino acids) and CH (330-440 amino acids) D.Binding to various cell types - Phagocytic cells, lymphocytes, platelets, mast cells, and basophils have receptors that bind immunoglobulins.This binding can activate the cells to perform some function.All immunoglobulins within a subclass will have very similar heavy chain constant region amino acid sequences.Again these differences are most commonly detected by serological means. Immunoglobulin Types Immunoglobulins can also be classified by the type of light chain that they have.This fragment was called Fc because it was easily crystallized.