Immunological response Flashcards
What is an antigen?
Is a substance that evokes the production of antibodies.
What is an antibody?
Is a receptor that binds to a specific antigen, to
destroy or neutralize a foreign invader or substance.
What is phagocytosis?
A process by which phagocytes engulf other
cells or particles. The foreign substances are destroyed
through different steps.
What is a B cell?
A lymphocyte that expresses membrane-bound antibodies
- plasma cells
- memory cells
What is a T cell?
T cell: A lymphocyte that expresses a T-cell receptor, CD3, and CD4 or
CD8. Several distinct T-cell subpopulations are recognized.
What is an NK cell?
A class of lymphocytes that do not have T- or B-cell receptors
- kill tumor cells
- express cell-mediated cytotoxicity
What is a neutrophil?
Circulating, phagocytic cells that are involved early in the
inflammatory response
- cell-mediated cytotoxicity
What is a monocyte?
Circulates in the bloodstream, migrate into tissues and
differentiate into macrophages.
What is a macrophage?
Are dispersed throughout the body
-phagocytic cell
-tissues (fixed macrophages)
-motile
What is a dendritic cell?
Phagocytic cells. Express class II MHC molecules and
co- stimulatory receptors → more potent antigen presenting cells
than macrophages and B cells.
What does the dendritic cell do after capturing the antigen?
After capturing antigen in the tissues, the dendritic cells migrate
into the blood or lymph and circulate to various lymphoid organs,
where they present the antigen to T cells.
What are the 4 defensive barriers of innate immunity?
Anatomic barrier- Skin, mucous membranes, normal flora
* Physiologic barrier - Temperature, pH, soluble factors
* Phagocytic barrier – Phagocytosis
* Inflammatory barrier – Inflammatory reactions
What are the four characteristics of adaptive immunity?
Four characteristic attributes:
* Antigenic specificity
* Diversity
* Immunologic memory
* Self/nonself recognition
What are the two important major groups of cells in adaptive immunity?
-Lymphocytes (B cells and T cells)
-Antigen-presenting cells (macrophages, B cells and dendritic cells)
What does T helper cells express?
CD4
What does T cytotoxic cells express?
CD8
What does T regulatory cells express?
FOXP3 transcription factor
What is the immune system of the digestive tract called?
The immune system of the digestive tract is called gut-associated
lymphoid tissue (GALT).
Mention some organised structures that are part of the immune system but found in the GI tract
organized structures
such as peyer ́s patches (small intestine), mesenteric lymph nodes
(mesentery), follicles (small and large intestine).
Can the epithelial cells deliver foreign antigens from the lumen to the
lymphoid tissue?
Yes
What is the TLR4 receptor also known as?
TLR4 is known as the LPS receptor (Gram-negative bacteria)
What does the TLR2 receptor do?
TLR2 recognizes bacterial lipoproteins and peptidoglycans (Gram-positive
bacteria)
What does the TLR receptors do in a healthy individual?
TLR signalling protects the intestinal epithelial barrier and confers
commensal tolerance.
What does the TLR receptors do in disease?
aberrant TLR signalling may stimulate diverse inflammatory
responses.
How can signals from bacteria be transduced to immune cells?
-Through receptors on epithelial cells such as MHC I and II molecules, and Toll-
like receptors (TLRs), signals from bacteria can be transduced to immune cells.
Through bacterial-epithelial cell interactions, probiotics can affect both the
innate and adaptive immune system, mention some.
- When presented by dendritic cells, the probiotic bacteria can modify the
activity signal in T cells and change the production of cytokines. - The cytokine pattern produced by macrophages can be changed.
- Up and down-regulation of membrane receptors can affect the signal
transduction (stronger or weaker). - Some strains can promote the differentiation of B cells into plasma cells
and increase the production of secretory IgA. - Through the activation signal, the probiotic bacteria can affect the number
of T cell subsets, e.g. regulatory T-cells. - By changing the composition of the intestinal microflora, probiotics can
modify the stimulation of the pattern recognition receptors, e.g. more LPS
in lumen will stimulate an inflammatory reaction. - By minimizing bacterial translocation, the immune system will be less
affected by Gram-negative bacteria. - By stimulating the production of mucus, the epithelial cells will be
protected from bacterial stimulation.
