Immunopathology 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
immune system consists of?
effector cells and substances
provide protection to an individual
following antigenic challenge
effector cells and substances
two responses of the immune system:
✓ humoral response
✓ cellular response
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
antigens is also known as?
immunogens
are macromolecules that are either natural or synthetic in origin that are capable of inducing immune response. They are usually microbial or foreign proteins or polysaccharide
antigens
are simple molecules that bind to performed 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 Cell (APC)
are specific clones of white blood cell
lymphocytes produced in the bone
marrow.
B-lymphocytes or B-cells
undergo a series of transformation into an antibody secreting plasma cell
through the aid of inducer T-
lymphocytes
sensitized B cells
contain the antigen binding sites, and a fragment labeled
Fab
that contains receptors for complement and effector cells
Fc
Enzyme studies showed that there are two fragments. What are these two?
Fab and Fc
Two types of lymphocytes are recognized;
✓ B Lymphocytes
✓ T Lymphocytes
that largely produce the
antibodies
B lymphocytes
that mediate cellular reactivity
T lymphocytes
are
by no means a homogenous
population like the B-cells
T-lymphocytes (T-cells)
There are two functional classes of T
cells:
✓ helper/inducer T cells
✓ cytotoxic/suppressor T-cells
Activated T cells secretes what?
interleukin-2
(IL-2 or T cell growth factor) that
stimulates the production of IL-2 receptors and the proliferation of T
cells
The helper T cells also secretes?
IL-4, IL-5, and IL- 6 (B cell growth
factors) that promote the proliferation and maturationof B cells.
showed that the two major classes of T cells could be distinguished one from the other
Surface Marker Studies
Helper cells
CD4 positive T cells
cytotoxic/suppressor T cells
CD8 positive cells
are surface glycoproteins that functions as adhesion molecules and as co-receptors for antigen.
CD4 and CD8
The ability of the animal body’s
immune system to distinguish _________
from ___________is one of the most fascinating features of the immune system
self from nonself
Studies of the immune reactions towards organ transplantation showed this capability is under fine control in specific locus of the genes called?
the major histocompatibility complex
In humans, this locus is located at chromosome 6 and is called?
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. What are these?
✓ Class I Antigen
✓ Class II Antigen
✓ Class III Antigen
are glycoproteins present on all nucleated cells and platelets
Class I Antigen
exist as bimolecular protein complexes restrictedly found in antigen presenting cells (monocytes,
macrophages, dendriticcells), B cells,
and some activated T cells
Class II Antigens
antigen presenting cells
monocytes, macrophages and dendritic cells
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 III Antigens
it regulates the cell-to cell
interaction in the immune
responses
MHC
facilitate interactions among
lymphocytes and between lymphocytes and
macrophages in the process of
immune recognition
Class II Antigens
are able to recognize antigens only in the form of antigenic peptide complexed with Class II antigens on the surface of antigen presenting cells
T helper Cells (CD4+)
recognize antigens presented on the
surface as antigenic peptide
complexed with Class I MHC
molecules
cytotoxic T cells
activated antigen presenting cells
macrophages, dendritic cells and Langerhans cells
When an antigen gains entry into
the animal body, it is first ingested and
processed by activated antigen
presenting cells
into antigenic fragments that expresses?
epitopes or its antigenic
determinants
composed of surface membrane
bound monomeric IgM programmed
during B cell maturation in the gut
associated lymphoid tissues in
mammals
B cells receptor for antigens
are antibody-like molecules located on the surface membrane, and is
programmed during cellular maturation of the T cells at the thymus
receptor for T cells
it is coded for by DNA rearrangement of coding segments to produce the receptor diversity
B cell receptors
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
It is the main effector pathway of the
immune response and has a receptor
unit able to recognize antibody
molecules
complement
The complement components are
labeled
C1, C2, C3, C4, C5, C6, C7, C8
and C9
activated via two pathways:
classical and alternate pathway
is initiated by the binding of
antigen antibody complexes to C1
that self-activates and cleaves C4
and C2 into C3convertase
classical pathway
C3 splits into two fragments
C3a and C3b
is released and increases vascular
permeability
C3a
forms a complex called C5 convertase that splits C5 into C5a and C5b
C3b
increases vascular permeability and attracts
polymorphonuclear and mononuclear leucocytes
C5a
initiates the terminal sequence C5b-C9 forming the membrane attack comple
C5b
that effect irreversible lesions
on cell membranes leading to cytolysis
membrane attack complex (mac)
the alternate pathway is initiated by a variety of substances including?
✓ bacterial polysaccharides
✓ zymosan
✓ lgA
is a generic term for polypeptide messenger molecules secreted lymphoid and non-lymphoid cells that mediates and regulates the growth, differentiation, and function of cells involved in immunity, hemopoiesis and inflammation
cytokines
are cytokines secreted by lymphocytes
lymphokines
are cytokines secreted by macrophages and
monocytes
monokines
is a cytokine that carries messages
between lymphocytes.
interleukin
are chemotactic cytokines produced by macrophages, monocytes and
T cells that attract leucocytes
to the site of inflammation or
infection
chemokines
The paramount function of the immune system is to?
✓ recognize foreign antigens
✓ protect the individual
These responses that result in tissue injury are called
hypersensitivity reactions
(allergic or immunopathologic
reactions)
the release of these could cause tissue injuries;
✓ vasoactive substances,
✓ phagocytosis or lysis of cells
✓activation of
inflammatory and cytolytic components of complement, ✓ and release of proteolytic enzymes,
✓ cytokines
✓ other mediators of inflammation from participating inflammatory cells
is a
prominent component of this
reaction, and is an important
process in host defense
against viral and fungal infections, and inspontaneous tumor rejection.
cytotoxicity
Type IV is involved in clinically diverse
conditions such as?
✓ allergic
contact dermatitis
✓ tuberculin hypersensitivity
✓ organ and
tissue transplant rejection
✓ graft-vs-host disease
A more common example of type IV reaction includes?
✓ flea allergy
✓ allergic contact dermatitis in
dogs and cats
Untoward immune response
towards administration of drugs
is called?
adverse drug reaction
The basic mechanisms are those described under hypersensitivity states, and the condition is considered if it meets the followingcriteria:
- The onset of hypersensitivity
state does not occur until sometime after initial exposure to a drug - After the reaction has been
established, the same may be
elicited by minute amount of the
drug in question; - The same reaction recur upon
repeated exposure to the same drug; - The reaction does not
resemble the known pharmacological action of the
drug; - The symptoms are suggestive
of known forms of hypersensitivity reaction
There are several predisposing factors for the development of ADR, and these include;
✓ host factor
✓ drug factor
✓ route of administration
✓ dose duration of exposure.
in this factor, the genetic composition may determine the difference in drug metabolism that may be related to
hypersensitivity to certain
metabolites of the drug, the differences in the capacity to respond to an immune challenge, the difference in tissue receptor sites, and the elaboration of
mediators of the immune system
that causes the variations in the
severity of hypersensitivity reactions.
host factor
in this factor, the tendency of a drug to induce immune response that results in a hypersensitivity reaction depends on the capacity of the
drug or its metabolites to act as or form a complete antigen or hapten. The route of application of the drug, its dose and duration of therapy may influence ADR. Topical application of drugs has the greatest capacity to induce ADR
followed by intravenous, intramuscular and oral route
drug factors
is defined as a failure of the individual to
recognize its own tissues thus
resulting to immune recognition
and consequent immune
reactions.
autoimmunity
they shrouded the possibility of the immune system working against self as a cause of
disease;
✓ Burnet’s clonal selection hypothesis
✓ Erlich’s “horror autotoxicus”
✓ the introduction of Koch’s postulate on the causation of disease
arises when there is a disordered regulation and interaction of the T cells and the B cells in response to an
antigenic challenge or stimulation
autoimmunity
involves a balance between the activity of suppressor T cell clones and
inducer T cell clones
central mechanism
the sensitizing antigens
self-antigens
Most self-antigens
autoantigens
There are several reactions
involving bypass of T cell specificity in the presence of competent B cell that result to the production of auto antibodies and include the following:
- Binding of foreign haptens as
drugs to host tissues - Infections by viruses and bacteria that alter host autoantigens
- Exposure to altered or cross-
reacting antigens - Stimulation of competent B cell by bacterial lipopolysaccharide
- Non-specific stimulation of
inducer T cell activity by adjuvant
in vaccines - Graft-versus-host
reaction