L1- Cells and Tissues of Immune System Flashcards
What is immunological recognition?
Presence of an infection must be detected (by the innate and adaptive immune systems)
What is the purpose of immune regulation?
Limits damage to the host by the immune response to
antigen (molecule capable of inducing an immune response). Failure of this regulation contributes to disease states including allergy and autoimmune
disease
What is immunological memory?
The adaptive immune system generates immunological memory – exposure to an infectious agent produces an immune response that can persist, and protect the host in a subsequent exposure
The immune response must full-fill which 4 main tasks?
- Immunological recognition: detection
- Contain infection/eliminate it via various effector functions
- Immune regulation: limit damage to host
- Immunological memory
Small resting B and T lymphocytes have not
yet encountered antigen; look identical. T or F?
True
When stimulated by an antigen, what happens to a lymphocyte?
Becomes an active lymphoblast which proliferate and differentiate to effector T and B lymphocytes
When B lymphocyte recognises soluble or cell surface antigens, they differentiate into what cells?
Plasma cells
What is the effector function of plasma cells? (B cells)
- Neutralizing the ability of microbes to infect target cells
- Labeling microbes (opsonizing) for phagocytosis
- Activating the complement pathway
Helper CD4+ T cells recognise antigen and secrete cytokines which stimulate what functions of immunity and inflammation?
- Activation of macrophages, to enhance phagocytosis
- Activation of B cells to produce antibodies
- Activation of CD8+ killer T cells
What is the effector function of CD8+ Cytotoxic T cells and NK cells?
To kill pathogens
What are the steps involved for macrophages to eradicate microbes via phagocytosis?
- Chemotaxis of phagocyte to microbes
- Adherence
- Ingestion of microbes by phagocytes into phagosome
- Phagosome and lysosome combine to form phagolysosome.
- Killing of microbes by reactive oxygen and nitrogen species and hydrolytic enzymes.
- Elimination (exocytosis)
Antigen is detected on macrophages with what class MHC molecule?
MHC Class II molecule presents peptide
on cell surface for surveillance by CD4+ T
What is the activated function of the neutrophil?
Phagocytosis and activation of bactericidal mechanisms
What are the primary lymphoid organs for B and T cells
Bone marrow for B cells and Thymus for T cells
List the second lymphoid organs involved in the presentation of foreign antigens to T and B cells to activate the adaptive immune system.
Spleen, Lymph nodes and mucosa-associated lymphoid tissue (MALT)
MALT includes: Waldeyer’s ring (tonsils and adenoids), lymphoid nodules, Peyer’s patch, urogenital lymphoid tissue, GALT (gut associated) mesenteric lymph nodes, BALT (bronchus-associated lymphoid tissue)
What is the purpose of the lymphatic system?
The lymphatic system is a drainage and filtration system that enables clear interstitial fluid and plasma proteins to flow back into blood. It is also a system for lymphocyte circulation and antigen presentation.
Where can you find the lymphatic system?
System present throughout body except cartilage and epidermis.
System starts as lymph capillaries (closed end) lymphatic vessels lymph node lymph duct blood.
Fluid flows only in one direction due to pressure from muscle action and one way valves. Lymph from all parts
of body enters blood stream via subclavian veins and thoracic duct.
Where do T and B cells originate and where do they mature?
•Both T and B lymphocytes originate in the bone marrow.
•B cells develop from lymphoid stem cells in foetal liver
hematopoietic tissue at 8-9 weeks
- Production moves to bone marrow where it continues through adult life
- Bone marrow is site of B cell development in mammals
- Precursor T cells migrate to thymus for maturation
Following antigenic stimulation in lymph node germinal centres,mature B cells can develop into…
Memory cells or antigen forming cells (plasma cells)
Explain what happens to T cells when they enter the thymus.
- Entry into thymus via high endothelial venules
- Migration to cortex
- T cell progenitors undergo proliferation and differentiation in cortex
- Mature T cells leave thymus via high endothelial venules and enter circulation
The thymus involutes with age. What is meant by this?
Involution of the thymus with replacement by adipose tissue.
• In humans atrophy begins at puberty and continues throughout life
- Involution begins within the cortex, which may disappear completely
- Cortical atrophy is very sensitive to corticosteroids; promoted by pregnancy and stress
• Likely that T cell generation within thymus does continue into adult life, at a much lower rate (keep with the homoeostasis of increasing memory B cells throughout life)
Naive lymphocytes enter lymph nodes via…
Blood through to the afferent lymphatic vessels
Lymphocytes and lymph return to blood via…
thoracic duct
Where is Peyer’s patch found?
lymphoid nodules found throughout small intestine (ileum)
