Immunology Flashcards
1
Q
What are the primary lymphoid organs? What is their major role?
A
- (primary lymphoid organs are where lymphocytes are formed and matured)
- 2 primary lymphoid structures: bone marrow and the thymus
- bone marrow: site of T and B cell formation; site of B cell maturation
- thymus: site of T cell maturation
2
Q
What are the secondary lymphoid organs?
A
- (secondary lymphoid organs are essentially filters that monitor the body’s fluids and organs for any pathogens; they are the sites of lymphocyte activation)
- lymph nodes and vessels, spleen, tonsils, Peyer’s patches, MALT
3
Q
What are the three major parts of a lymph node? What is found/what occurs in each?
A
- follicle, paracortex, and medulla
- follicle: (outer portion of cortex) site of B-cell localization and proliferation
- paracortex: (inner portion of cortex) houses T-cells
- medulla: site of lymph flow from afferent lymphatic to efferent lymphatic; contains medullary sinusoids and medullary cords (sinusoids are passages for lymph flow and contain macrophages and reticular cells; cords are lymphatic tissue made up of Ab-secreting plasma cells and lymphocytes)
4
Q
What does the right lymphatic duct drain? The left lymphatic duct?
A
- right lymphatic duct drains the right side of the body that lies above the diaphragm (includes the right upper limb)
- left lymphatic duct drains everything else (it arises from the thoracic duct, which essentially drains the lower half of the body and abdomen via the cisterna chyli)
- each duct drains into the junction between the left or right subclavian and internal jugular veins
5
Q
Which lymph nodes drain each part of the body?
A
- head and neck: cervical nodes
- lungs: hilar nodes
- trachea and esophagus: mediastinal nodes
- upper limb, breast, skin above umbilicus: axillary nodes
- liver, stomach, spleen, pancreas, upper duodenum (foregut): celiac nodes
- lower duodenum, jejunum, ileum, colon to splenic flexure (midgut): superior mesenteric nodes
- colon from splenic flexure through anal canal (hindgut): inferior mesenteric, internal iliac, and superficial inguinal nodes
- bladder, vagina, prostate: internal iliac nodes
- testes, ovaries, kidneys, uterus: para-aortic nodes
- skin below umbilicus: superficial inguinal nodes
- dorsolateral foot, posterior calf: popliteal nodes (these areas are not drained by the superficial inguinal nodes even though they are below the umbilicus)
6
Q
What makes up the red and white pulps of the spleen? What is found in between the two pulps?
A
- red pulp: RBCs
- white pulp: T-cells (in the periarterial lymphatic sheath) and B-cells (in follicles/germinal centers)
- the marginal zone (between the red and white pulp) contains APCs
7
Q
Which organisms is an asplenic individual susceptible to? Why?
A
- encapsulated organisms
- asplenic patients have decreased levels of IgM, which means a lowered ability to activate complement, which means decreased opsonization (opsonization is needed to phagocytose encapsulated organisms)
- SHiNE SKiS: Strep pneumoniae, Hib, Neisseria meningitidis, Escherichia coli, Salmonella, Klebsiella pneumoniae, Strep agalactiae (group B strep)
8
Q
Quickly compare innate and adaptive immunity.
A
- innate: nonspecific; rapid response (minutes to hours); neutrophils, macrophages, monocytes, complement, dendritic cells, NK cells; recognizes pathogenic PAMPs (pathogen-associated molecular patterns) via TLRs (a type of pattern recognition receptor, PRR)
- adaptive: highly specific; develops over long periods, but subsequent exposures trigger faster and more robust responses; T-cells, B-cells, antibodies; recognizes pathogens via APCs and memory cells
9
Q
What is MHC? What is its major purpose?
A
- major histocompatibility complex; 2 classes: types I and II
- humans have HLA (human leukocyte antigen)
- MHC is needed to present antigen fragments to T-cells in order to trigger an adaptive immune response; it essentially allows for self-recognition vs. pathogen recognition
10
Q
MHC Class I; which cells have it? What does it bind to? Which type of antigen does it work with? What is its function?
A
- MHC class I (loci: HLA-A, HLA-B, and HLA-C)
- found on all nucleated cells of the host (RBCs lack nuclei, so they lack MHC I)
- binds to T-cell receptor (TCR) and CD8
- function: presents endogenously synthesized antigens of its own cell (self-antigens, viral antigens, etc.) to CD8+ cytotoxic T-cells
11
Q
MHC Class II; which cells have it? What does it bind to? Which type of antigen does it work with? What is its function?
A
- MHC class II (loci: HLA-DR, HLA-DP, HLA-DQ)
- found ONLY on APCs (macrophages, dendritic cells, B-cells, Langerhans cells in skin)
- bind to T-cell receptor (TCR) and CD4
- function: presents exogenously synthesized antigens gathered from the body (bacteria, etc.) to CD4+ T-helper cells
12
Q
What are NK cells? How do they work? What do they target? How are they activated? Are they lymphocytes or monocytes?
A
- NK cells are natural killer cells
- they use perforin and granzymes to induce apoptosis in targeted cells
- they target cells LACKING MHC I (tumor cells, virally infected cells)
- MHC I binds to the NK cell’s inhibitory receptors (CD16), so without this signal, the NK cell gets activated
- NK cells are also activated via antibody-dependent cell-mediated cytotoxicity (NK cell’s CD16 binds to Fc portion of bound IgG, triggering its activation)
- they are lymphocytes, but are part of innate immunity!
13
Q
In very simple terms, what are the major functions of B- and T-cells?
A
- B-cells: recognize antigen and undergo somatic hypermutation to optimize antigen specificity; produce antibodies as plasma cells; maintain memory as memory B-cells
- CD4+ T-cells: (helper T-cells) assist B-cells to make antibodies, release cytokines that activate other immune cells/responses
- CD8+ T-cells: (cytotoxic T-cells) directly kill virus-infected cells, neoplastic cells, donor-graft cells by inducing apoptosis
14
Q
What happens to naive T-cells in the thymic cortex? What about in the medulla?
A
- in the thymic cortex, naive T-cells undergo positive selection: those that have TCRs able to recognize MHC molecules will SURVIVE (because MHC recognition is the basis for how these cells function)
- those that survive move onto the medulla
- in the medulla, they undergo negative selection: those that have TCRs with high affinity for self antigens will undergo APOPTOSIS (this creates self tolerance)
15
Q
How many signals are needed for T-cell activation? B-cell activation? What are they for each?
A
- both cell types require 2 signals to be activated
- helper T-cells: APC’s MHC II-antigen complex binds to TCR + APC’s B7 binds to T-cell’s CD28
- cytotoxic T-cells: infected cell’s MHC I-antigen complex binds to TCR + B7 binds to CD28
- B-cells: B-cell’s MHC II-antigen complex binds to helper T-cell’s TCR (remember B-cells are also APCs!) + B-cell’s CD40 receptor binds to helper T-cell’s CD40 ligand
