IMMUNOPATHOLOGY 6 Flashcards
primarily serves to defend the animal body against infections.
immune system
These untoward responses of the immune system that result
to tissue injuries are called
immunopathologic reactions
is the study of diseases caused by or resulting from immune mechanisms, and is
concerned primarily with untoward consequences of immune reactions.
immunopathology
The immune system consists of
effector cells and
substances that provide
protection to an individual
There are two responses
of the immune system:
humoral response
cellular response
e mediated largely by antibodies and other effector substances such as complement,
humoral response
mediated by sensitized lymphocytes and cells of the reticulo-endothelial system.
cellular response
(also known as immunogens)
Antigens
are macromolecules that are either natural or synthetic in origin that are capable of inducing immune response.
-are usually microbial or foreign proteins or polysaccharide
Antigens
are simple molecules that bind to preformed antibodies or sensitized immune cells and can
induce an immune response when coupled to a carrier protein.
Haptens
usually, macrophages and dendritic cells process the antigen and present the
same to B lymphocytes
antigen presenting cells (APC)
The sensitized B-cells undergo a series of transformation into an antibody secreting plasma cell through the aid of inducer T-lymphocytes
(another lymphocyte clone subpopulation)
The plasma cells synthesize the antibody, a plasma protein belonging to the gamma globulin fraction of serum
next two are found on mucosal surfaces and body secretions
IgA and IgD
The first two have their greatest
concentration in the plasma,
IgG and IgM
specific clones of white
blood cell lymphocytes
produced in the bone marrow.
B-lymphocytes or B-cells
surface bound to specific cells such asbasophils and mast cells.
IgE
An antibody molecule consists of :
two identical heavy chains of amino acids and
two identical light chains chemically linked by disulfide bonds in Y configuration
The antigen-binding site at the Fab fragments bind specifically and selectively to the
determinants of the antigen molecule that initiated the production of the antibody.
Is a major humoral component of innate immunity and a
mediator of inflammation normally present in the plasma in inactive form that are
activated to mediate or amplify the reaction.
Complement
Enzyme studies showed that there are two fragments:
fab and fc
contain the antigen binding sites
Fab
that contains receptors for complement and effector cells
Fc
is mediated largely by sensitized lymphocytes.
cellular response
Two types of lymphocytes are recognized:
b cells
t cells
that mediate cellular
reactivity.
t cells
There are two functional classes of T
cells:
helper/inducer T cells and
the cytotoxic/suppressor T-cells
largely produce the antibodies
B-lymphocytes
The helper T cells also secrete IL -4, IL-5, and IL-6 (B cell growth factors) that promote the proliferation and maturation
of B cells.
Activated T cells secrete interleukin-2
(IL-2 or T cell growth factor) that stimulates the production of IL-2
receptors and the proliferation of T cells.
Helper cells are CD4 positive T cells,
cytotoxic/suppressor T cells are CD8 positive cells.
are surface glycoproteins that functions as adhesion molecules and as co-receptors for
antigen
CD4 and CD8
Studies of the immune reactions towards organ transplantation showed this capability is under fine control in specific locus of the genes called
major histocompatibility
complex
In humans, this locus is located at chromosome 6 and is called the
human lymphocyte antigen complex (HLA complex)
This chromosome region
codes for surface proteins in body cells called
histocompatibility antigens or transplantation antigens.
MHC gene products are classified into three categories:
are glycoproteins present on all nucleated cells and
platelets.
class I antigens
exist as bimolecular protein complexes restrictedly
found in antigen presenting cells (monocytes, macrophages, dendritic
cells), B cells, and some activated T cells.
class 2
are protein components of the complement system
(C2, C4 and Bf) that are coded for within the MHC. These proteins do not
function as histocompatibility antigens.
class 3
significantly influences immune reactivity.
It regulates the cell-to cell
interaction in the immune
responses (Figure 6.4-MHC
restriction on antigen
recognition)
MHC
Class II antigens
facilitate interactions among
lymphocytes and
between lymphocytes and
macrophages in the process of immune recognition.
T helper cells (CD4+) are able to recognize antigens only in the form of antigenic peptide complexed with Class II antigens on the surface of antigen presenting cells.
Cytotoxic T cells recognize antigens presented on the surface as antigenic peptide complexed with Class I MHC
molecules.
consists of plasma proteins belonging to the beta-globulin
fraction of the plasma and is normally synthesized by hepatocytes, macrophages,
and gut epithelial cells.
Complement
The complement components are labeled C1, C2, C3, C4, C5, C6, C7, C8
and C9.