#Shorts 3
Antibodies are also called immunoglobins. A very crude electrophoretic fractionation of
serum proteins separates albumin from other serum proteins collectively called globulins.
The globulins are also further characterised on the basis of charge such as α, β and γ -
globulins, γ-globulins being the most positively charged. This latter fraction was discovered
to be made up largely of antibody molecules. The existence of antibody secreting tumors
known an myelomas or plasmacytomas greatly facilitated the study of immunoglobulins and
their structure. Tumors are in general derived from a single cell. A single cell and its progeny
are generally referred to as a clone and tumors are therefore clonal (or Harvard-MIT
Division of Health Sciences and Technology HST.176: Cellular and Molecular Immunology
Course Director: Dr. Shiv Pillaimonoclonal) outgrowths. Myelomas and plasmacytomas are
derived from differentiated antibody secreting B lymphocytes known as plasma cells These
plasma cell tumors each produce large amounts of a single or monoclonal antibody.
The portions of the heavy chain and light chain are involved in antigen recognition are at the
N-terminal ends and are referred to as V domains. The remaining portions of the heavy and
light chains are referred to as C regions. Each light chain constant region contains a single
constant (CL) domain. A domain refers to a portion of a protein which can be separated
from the rest of the molecule and still fold into its correct shape. The domains in
immunoglobulin molecules have a typical three-dimensional structure which is now referred
to as an immunoglobulin domain and is found in a variety of proteins (many of which
existed before the evolution of immunoglobulins). Each heavy chain constant region is made
up of three or four domains (CH). The portion of each heavy chain that is associated with
the light chain is the VH domain and the CH1 domain. A cysteine residue in the CH1 domain
forms a covalent disulfide bridge with a cysteine residue towards the C-terminal end of the
CL domain. When one class of immunoglobulin molecules known as IgG molecules are
cleaved with a proteolytic enzyme called papain, these antibodies are cleaved into two
identical fragments known as Fab (Fraction antigen binding) fragments and a single Fc
(Fraction crystallizable) fragment. Cleavage with pepsin yields an F(ab)2 fragment and an Fc
fragment. Each Fab fragment corresponds to an arm of the antibody Y and is made up of a
light chain covalently associated (via a disulfide bridge) with a portion of the heavy chain
containing the VH and CH1 domains. The Fc portion corresponds to the stem of the Y and is
a dimer of the CH2 and CH3 domains of IgG covalently united via disulfide bridges between
the two heavy chains.
See full - HST 175 (mit.edu)
Antibodies are also called immunoglobins. A very crude electrophoretic fractionation of
serum proteins separates albumin from other serum proteins collectively called globulins.
The globulins are also further characterised on the basis of charge such as α, β and γ -
globulins, γ-globulins being the most positively charged. This latter fraction was discovered
to be made up largely of antibody molecules. The existence of antibody secreting tumors
known an myelomas or plasmacytomas greatly facilitated the study of immunoglobulins and
their structure. Tumors are in general derived from a single cell. A single cell and its progeny
are generally referred to as a clone and tumors are therefore clonal (or Harvard-MIT
Division of Health Sciences and Technology HST.176: Cellular and Molecular Immunology
Course Director: Dr. Shiv Pillaimonoclonal) outgrowths. Myelomas and plasmacytomas are
derived from differentiated antibody secreting B lymphocytes known as plasma cells These
plasma cell tumors each produce large amounts of a single or monoclonal antibody.
The portions of the heavy chain and light chain are involved in antigen recognition are at the
N-terminal ends and are referred to as V domains. The remaining portions of the heavy and
light chains are referred to as C regions. Each light chain constant region contains a single
constant (CL) domain. A domain refers to a portion of a protein which can be separated
from the rest of the molecule and still fold into its correct shape. The domains in
immunoglobulin molecules have a typical three-dimensional structure which is now referred
to as an immunoglobulin domain and is found in a variety of proteins (many of which
existed before the evolution of immunoglobulins). Each heavy chain constant region is made
up of three or four domains (CH). The portion of each heavy chain that is associated with
the light chain is the VH domain and the CH1 domain. A cysteine residue in the CH1 domain
forms a covalent disulfide bridge with a cysteine residue towards the C-terminal end of the
CL domain. When one class of immunoglobulin molecules known as IgG molecules are
cleaved with a proteolytic enzyme called papain, these antibodies are cleaved into two
identical fragments known as Fab (Fraction antigen binding) fragments and a single Fc
(Fraction crystallizable) fragment. Cleavage with pepsin yields an F(ab)2 fragment and an Fc
fragment. Each Fab fragment corresponds to an arm of the antibody Y and is made up of a
light chain covalently associated (via a disulfide bridge) with a portion of the heavy chain
containing the VH and CH1 domains. The Fc portion corresponds to the stem of the Y and is
a dimer of the CH2 and CH3 domains of IgG covalently united via disulfide bridges between
the two heavy chains.
See full - HST 175 (mit.edu)
