HISTO: Lymphatic System Flashcards
Specific lymphoid organs
Thymus, spleen, lymph nodes
MALT =
Mucosa-associated lymph tissue, in respiratory, reproductive and urinary system
GALT =
Gut-associated lymphatic tissue, e.g. Tonsils, Peyer’s patches and appendix. Aggregates of lymphocytes. e.g. Lamina propria (plasma cells)
All Lymphocytes originate in
Bone marrow
T lymphocytes mature in the
Thymus
Any substance that can induce a specific immune response is called an:
antigen
Immune cells react to small molecular domains of the antigen called:
Epitopes
An immune response is generated against a specific antigen, which can be:
- soluble substance (e.g., a foreign protein, polysaccharide, or toxin)
- an infectious organism, bacteria , protozoa, foreign tissue or transformed tissue
First line of defense against microbial aggression is by:
Innate immunity (non-specific)
The initial contact with antigen or foreign agent initiates a reactions that involve effector cells, and immunity conferred by “memory cells:
Adaptive immunity (specific)
Various secreted substances that neutralize foreign cells:
thiocyanate in saliva
lysozyme
interferon
complement in serum
Adaptive immunity induces _____ against antigens through somatic rearrangements of genes that encode immunoglobulins and specific receptors on T lymphocytes
acquired resistance
Production of proteins called antibodies that mark invaders for destruction by other immune cells is which type of defense?
Humoral immune response
Destruction of transformed and virus-infected cells, etc. by specific “killer” cells is which type of defense?
Cellular immune response
Lymphocytes T (approximately 60- 80%) in blood or lymph represent a circulating pool of:
immunocompetent cells
These cells exit the systemic circulation to enter the lymphatic tissue (surveillance).
T lymphocytes
This population (approximately 30%) migrate directly to the tissues and lymphoid organs:
B lymphocytes
Where a B lymphs found?
in the connective tissue that underlies the lining epithelium of the respiratory, gastrointestinal, and urogenital tracts
Are part of nonspecific (innate) immunity, are named for their ability to kill certain types of target cells. They constitute about 5% to 10% of circulating lymphocytes
NK cells (natural killer)
Participate as antigen presenting cells (APCs), that phagocytose and process antigens, attach them to MHC II and present them to T-cells
Supporting cells
Examples of Supporting cells:
Reticular cells
dendritic cells
macrophages
Langerhans cells
epithelioreticular cells
What are cluster of differentiation (CD) markers?
Membrane markers for cells in lymphatic tissue to identify
B-lymphocytes markers:
CD9, CD19, CD20
T-lymphocytes markers:
CD2, CD3, CD5, CD7, helper CD4+ and cytotoxic CD8+, CD40L
NK cells markers:
CD16, CD56 and CD94
products of a “supergene” located on chromosome 6 in humans
MHC I and MHC II
from major histocompatibility gene complex
Where are MHC I expressed?
Is expressed on the surface of all nucleated cells and platelets
Presents peptides fragments (8 to 10 amino acids in length) to cytotoxic CD8+ T lymphocytes.
MHC I
Where are MHC II expressed?
on a restricted population of cells known as antigen-presenting cells (APCs)
present exogenous (foreign) peptides (18 to 20 amino acids) to helper CD4+ T lymphocytes
MHC II
These cells are further subdivided by their ability to secrete cytokines
Helper CD4+ T lymphocytes
Which lymphocytes are MHC II restricted
CD4+ T
T lymph important surface markers
CD4 and CD8
synthesize interleukin 2 (IL-2), interferon γ (IFN-γ), and tumor necrosis factor α (TNF-α)
Helper TH1 cells
TH1 helper cells intercact with?
cytotoxic CD8+ T lymphocytes (CTLs), NK cells, and macrophages
interact with B lymphocytes and are essential for initiating antibody-mediated immune responses that control extracellular pathogens
Helper TH2 cells
What does TH2 synthesize?
IL-4, IL-5, IL-10, and IL-13
Their principal function is to destroy extracellular bacteria and fungi by recruiting neutrophils to the site of inflammation
Helper TH17 cells synthesize IL-17 and IL-22
What are defensins?
antimicrobial peptides
Kill other target cells such as virus-infected cells, cancer-transformed cells, cells infected with parasites, and transplanted cells.
Cytotoxic CD8+ T lymphocytes (CTLs)
Cytotoxic CD8+ T lymphocytes (CTLs) produce:
proteins called fragmentings and perforins that create holes in the cell membrane and induce apoptosis
Which lymphocytes are MHC I restricted
Cytotoxic CD8+ T lymphocytes (CTLs)
T lymphocytes that can functionally suppress an immune response to foreign and self- antigen by influencing the activity of other cells in the immune system
Regulatory (suppressor) T lymphocytes
regulatory cells that can diminish the ability of T lymphocytes to initiate immune responses:
CD4+CD25+FOXP3
Which gene can cause polyendocrinopathy, enteropathy, X- linked (IPEX) syndrome, recessive disorder characterized by dysfunction of the T regulatory (Treg)
Mutations of the FOXP3 gene
Represent a small population of T cells (<5%) with a distinct T cell receptors (TCRs) on their surface made of one γ chain and one δ chain
Gamma/delta (γ/δ) T lymphocytes
Where do Gamma/delta (γ/δ) T lymphocytes develop?
These cells develop in the thymus and migrate into various epithelial tissues (e.g., the skin, oral mucosa, intestines, and vagina).
Which lymphs participate in humoral immunity?
B lymphs
B cells express which molecules on the cell surface?
major histocompatibility complex II (MHC II)
During differentiation, the BCR isotope switches from ___ to ___
immunoglobulin M (IgM) in immature B cells to a mixture of immunoglobulin D (IgD) and IgM in mature
what are Immunoglobulins?
Antibodies that are circulating plasma glycoproteins that interact with specific antigen
Late stage in differentiation of B-lymphocytes
plasma cells
where are plasma effector cells found?
Abundant in medullary cords of lymph nodes, marginal zone and cords of spleen and connective tissue
A few antigen-specific B lymphocytes remain in circulation as:
memory cells
IgG function:75-80%
Longest half- life (23 days) of all five. Stimulates chemotaxis. Activates complement. Crosses the placenta
IgM function:5-10%
Produced in initial immune response. Activates complement system and macrophages
IgA function:10-15%
Glandular secretions: saliva, tears, milk, mucus. Aids in defense against microbes and foreign molecules penetrating body via cell linings of these cavities
IgD function:
In the membrane of lymphocytes. Acts as an antigen receptor on surface of mature B lymphocytes