6 Immnnoproteins
6.1
6.2
6.2.1
6.2.2
6.2.3
6.2.4
6.3
6.4
6.5
6.6
The Immunoglobulin Super-Family
Immunoglobulins
Basic Structure of Immunoglobulins
The Variety of Immunoglobulins
Comparative Biochemistry of Immunoglobulins
Evolution of the Immunoglobulins
T Cell Receptors
MHC Antigens and ~z-Macroglobulins
Cytokines and Interferons
The Complement System
All cells are able to communicate with the environment, i.e. receive signals from their surroundings and broadcast their (immunological) identity
to the outside. The registration of signals is via
receptors on the surface; for example, there are
receptors for hormones or neurotransmitters and
also for the recognition of other cells as "self" or
"non-self". Foreign cells or substances induce
specific defence reactions (immune responses).
In both the vertebrates and invertebrates,
immune responses may involve certain blood cells
(cell-mediated immunity) or soluble proteins of
the plasma (humoral immunity). In accordance
with the general aims of this book, the emphasis
of the account that follows is placed on the comparative biochemistry and evolution of the proteins involved in the immune response. However,
their functions cannot be understood without
some basic knowledge of cell biology.
Of the various cell types in the blood and other
extracellular fluids, the Band T lymphocytes and
the macrophages are the most important for the
responses of man and other mammals to molecular structures (antigens) recognized as foreign.
Soluble macromolecular antigens in the blood
can induce an immune response only after they
are taken up by macrophages or other antigenpresenting cells (APCs) and subsequently "presented" to the B lymphocytes or certain T lymphocytes (T helper cells). The antigen is proteolytically cleaved into fragments in the APCs prior
to presentation. Low molecular weight substan6.7
Lectins
6.8
Humoral Defence in Invertebrates
6.9
Immune-Reactive Proteins of the Cell Surface
6.9.1 Cell-Adhesion Molecules of Vertebrates
6.9.2 Cell-Binding Proteins of Invertebrates
6.9.3 The Variable Surface Glycoproteins
of the Trypanosomes
6.9.4 Surface Proteins of Other Protozoa
References
ces can function as antigens only when they occur
as haptens bound to a "self" protein. Each B
lymphocyte carries on its surface immunoglobulin
molecules of one of the many existing structural
variants. These function as receptors for the corresponding (complementary) antigen. There is a
special type of receptor on T lymphocytes. T helper cells can recognize an antigen only when it is
presented on the surface of an APC together with
an Ia antigen, which is the product of a class II
MHC (major histocompatibility complex) gene.
In collaboration with the APCs and the T helper
cells, the B cells specific for the antigen are
induced to proliferate; fully differentiated plasma
cells are produced and these synthesize and secrete large quantities of antibodies. The soluble
immunoglobulins produced by the plasma cells
bind to the complementary antigens on the surface of cells which are then destroyed (lysed) by
the complement system. Soluble antigens associate with the complementary immunoglobulins to
form large molecular complexes, which bind to
specific receptors on neutrophil blood cells and
natural killer (NK) cells and are thereby removed
from the circulatory system [159].
Cell-mediated immunity requires the activation of the cytotoxic T cells and phagocytic macrophages. The extent of the response is determined by T helper and suppressor cells. The cytotoxic T lymphocytes only destroy cells which carry
the self MHC-class-I antigen in addition to the
foreign antigen, e.g. virus-infected cells of the
6.1
6.2
6.2.1
6.2.2
6.2.3
6.2.4
6.3
6.4
6.5
6.6
The Immunoglobulin Super-Family
Immunoglobulins
Basic Structure of Immunoglobulins
The Variety of Immunoglobulins
Comparative Biochemistry of Immunoglobulins
Evolution of the Immunoglobulins
T Cell Receptors
MHC Antigens and ~z-Macroglobulins
Cytokines and Interferons
The Complement System
All cells are able to communicate with the environment, i.e. receive signals from their surroundings and broadcast their (immunological) identity
to the outside. The registration of signals is via
receptors on the surface; for example, there are
receptors for hormones or neurotransmitters and
also for the recognition of other cells as "self" or
"non-self". Foreign cells or substances induce
specific defence reactions (immune responses).
In both the vertebrates and invertebrates,
immune responses may involve certain blood cells
(cell-mediated immunity) or soluble proteins of
the plasma (humoral immunity). In accordance
with the general aims of this book, the emphasis
of the account that follows is placed on the comparative biochemistry and evolution of the proteins involved in the immune response. However,
their functions cannot be understood without
some basic knowledge of cell biology.
Of the various cell types in the blood and other
extracellular fluids, the Band T lymphocytes and
the macrophages are the most important for the
responses of man and other mammals to molecular structures (antigens) recognized as foreign.
Soluble macromolecular antigens in the blood
can induce an immune response only after they
are taken up by macrophages or other antigenpresenting cells (APCs) and subsequently "presented" to the B lymphocytes or certain T lymphocytes (T helper cells). The antigen is proteolytically cleaved into fragments in the APCs prior
to presentation. Low molecular weight substan6.7
Lectins
6.8
Humoral Defence in Invertebrates
6.9
Immune-Reactive Proteins of the Cell Surface
6.9.1 Cell-Adhesion Molecules of Vertebrates
6.9.2 Cell-Binding Proteins of Invertebrates
6.9.3 The Variable Surface Glycoproteins
of the Trypanosomes
6.9.4 Surface Proteins of Other Protozoa
References
ces can function as antigens only when they occur
as haptens bound to a "self" protein. Each B
lymphocyte carries on its surface immunoglobulin
molecules of one of the many existing structural
variants. These function as receptors for the corresponding (complementary) antigen. There is a
special type of receptor on T lymphocytes. T helper cells can recognize an antigen only when it is
presented on the surface of an APC together with
an Ia antigen, which is the product of a class II
MHC (major histocompatibility complex) gene.
In collaboration with the APCs and the T helper
cells, the B cells specific for the antigen are
induced to proliferate; fully differentiated plasma
cells are produced and these synthesize and secrete large quantities of antibodies. The soluble
immunoglobulins produced by the plasma cells
bind to the complementary antigens on the surface of cells which are then destroyed (lysed) by
the complement system. Soluble antigens associate with the complementary immunoglobulins to
form large molecular complexes, which bind to
specific receptors on neutrophil blood cells and
natural killer (NK) cells and are thereby removed
from the circulatory system [159].
Cell-mediated immunity requires the activation of the cytotoxic T cells and phagocytic macrophages. The extent of the response is determined by T helper and suppressor cells. The cytotoxic T lymphocytes only destroy cells which carry
the self MHC-class-I antigen in addition to the
foreign antigen, e.g. virus-infected cells of the