2 - Cells and Tissues of the Immune System Flashcards
What is the evolutionary purpose of the immune system?
To prevent and eradicate infections that we’ve already come across, but also that we’ve yet to cross paths with and cannot predict.
Define infection What types of species are infectious?
Invasion and multiplication of one species in the body of a second species at the expense of the second species.
Viruses, bacteria, fungi, eukaryote parasites.
Which cells are phagocytes?
Neutrophils
Monocytes
Macrophages
Dendritic cells
Which cells are granulocytes?
Eosinophils
Basophils
Mast cells
What white blood cells are lymphocytes?
T helper cells Cytotoxic T cells Regulatory T cells B cells Plasma Cells
Where do immune cells originate before and after birth? When does this occur?
WBC development begins 23 days post-fertilization in fetal liver where stem cells colonize.
At ~10.5 weeks post-fert, progenitor stem cells colonize the bone marrow.
After birth they only originate from bone marrow.
What are generative (primary) lymphoid organs? What is their function?
Bone marrow and thymus.
Where T and B cells mature and become competent to respond to antigens.
What are peripheral (secondary) lymphoid organs? What is their function?
Lymph nodes, spleen, mucosal and cutaneous lymphoid tissues.
Where T and B cell responses to antigens are initiated.
What is the thymus?
A glandular organ located behind the sternum between the lungs.
T cell progenitors (aka thymocytes) enter the thymus and exit as either helper T cells (aka TH cell or CD4+ T cell) or cytotoxic T cells (TD or CD8+ T cell).
What is a naive T cell? What is a memory T cell? How do their levels change as thymus output decreases (ie with age)?
Naive T cells: have never encountered its cognate antigen
Memory T cell: has encountered cognate antigen
Naive cells decrease with age and memory T cells increase with age.
What is an immune privileged organ? What are examples?
Organs that contain few, if any, leukocytes.
Brain, eyes, ovaries, testes, uterus, fetus.
Evolutionarily, the fitness cost of inflammation in these organs is too high. An immune response there would be too damaging.
Leukocytes travel to tissues via ______ and exit via _____.
travel to tissues via vasculature and exit via lymphatics.
Lymphatics eventually deliver fluid back to vasculature via the thoracic and right lymphatic duct.
What directs the movement of lymph?
Mainly contraction of skeletal muscles.
Pulses in arteries.
What are lymph nodes? What do they contain?
Encapsulated structures that interrupt the course of lymphatic vessels that are well-suited to detect pathogens from draining tissues.
Contain T and B cells.
When do lymph nodes get enlarged?
When the draining tissue is infected.
What are antigen presenting cells (APCs)? How do they enter and exit the lymph node?
Leukocytes that engulf antigens in tissues and travel through lymphatics to introduce (present) the antigen to T and B cells.
Enter via afferent lymphatic vessel, exit via efferent lymphatic vessel.
How do T and B cells enter and exit the lymph node?
Through high endothelial venules (HEVs) which connect to the vasculature,.
What is the organization of T and B cells in lymph nodes in the absence of an infection?
T cells reside in the T cell zone, also called the parafollicular cortex (middle)
B cells reside in the B cell zone, also called the lymphoid follicle (outside).
What are germinal centers?
Specialized structures in lymphoid organs that develop during T-dependent B cell responses.
Occurs when T and B cells interact.
What is the spleen?
A highly vascularized organ that captures pathogen products present in the blood.
The spleen is to vasculature as the lymph node is to lymphatics.
What is the location of the spleen called where leukocytes are concentrated? What is the organization?
White pulp: the structural units of immunity in the spleen.
B cells around the perimeter in B cell zones and T cells in center.
What separates the white and red pulp of the spleen?
The marginal zone.
How are the T cells of the spleen organized?
They form a pariarteriolar lymphoid sheath (PALS) around a center arteriole.
What are MALT, SALT, and BALT? What do these have in common?
Mucosa-associated lymphoid tissue.
Skin-associated lymphoid tissue
Bronchus associated lymphoid tissue
They’re specialized lymphoid tissue that exit in locations with the highest exposure to microorganisms.
Where can MALT, SALT, and BALT be found? How are they organized?
Under the epithelia of the GI tract, skin epithelia, and respiratory tract.
Organized in a similar way as lymph nodes.
What is the most specific way to classify immune cell types?
Cluster of differentiation (CD) system - which has numerical designations.
Each CD represents a unique cell surface protein.
What is the purpose of flow cytometry? How does it work?
Used to measure frequency of each type of cell (ie the basis for the CBC with WBC differential).
Complex mixture of cells is treated with CD-specific fluorophore-conjugated antibodies and run in a flow cytometer so lasers can activate the fluorophore and detectors measure the presence or absence on each cell.
What is an adjuvant?
A substance present in the same environment as the antigen, and promotes the generation of an antigen-specific immune response (eg bacterial products).
What is the function of humoral (adaptive) immunity?
Block infections and eliminate extracellular microbes via B lymphocytes.
What is the function of cell-mediated (adaptive) immunity?
Elimination of phagocytosed microbes via helper T lymphocytes.
Kill infected cells and eliminate reservoirs of infection via cytotoxic T lymphocytes.
What is a vaccine?
An antigen/adjuvant mixture used to stimulate production of antibodies and provide immunity against one or several diseases.
Used to act as an antigen without inducing the disease.
What do vaccines do to the body?
Initiate a primary antibody response and in some cases, a secondary and tertiary response (boosters) so a person has increased protection.
