Term
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Definition
mucosa-associated lymphoid tissue
NON-ENCAPSULATED, lymphocytes or lymphoid nodules, located under an epithelial layer
TONSILS
BALT: bronchus-associated lymphoid tissue
-composed of lymphoid nodules found most predominately in regions where a BRONCHUS splits to form BRONCHIOLES
-most cells are B CELLS, though some T cells and APCs are found in BALT
GALT: gut-associated lymphoid tissue
-when follicles become aggregated in the lamina propria of the ILEUM of the GI tract, they're called PEYER'S PATCHES
--PP are composed of CENTRAL B CELLS, surrounded by LOOSE T CELLS, APC (antigen-presenting cells), and M (microfold) cells |
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Term
Identify the histological characteristics, cell components, importance, disorders, functions of:
loose (diffuse) lymphoid tissue |
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Definition
not sharply delineated, no special organization
in the LAMINA PROPRIA of GI & respiratory tracts
macrophages, lymphocytes, reticular cells
RETICULAR STROMA provides STRUCTURE |
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Term
Identify the histological characteristics, cell components, importance, disorders, functions of:
lymphoid nodules (follicles)
-primary
-secondary |
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Definition
lymphoid nodules can be in dense aggregations or as spherical masses, esp B LYMPHOCYTES
NON-ENCAPSULATED, scattered in GI and respiratory systems
Primary: no germinal centers, mainly B LYMPHOCYTES, which differentiate into PLASMA CELLS after stimulation by T HELPER CELLS
Secondary - contains a GERMINAL CENTER which appears light, forms as an ANTIGENIC response, contains LYMPHOBLASTS & PROLIFERATING B LYMPHOCYTES
-are TRANSITORY
-OUTER CORONA is darker stained than germinal center (b/c it primarily contains newly-formed, IMMATURE B LYMPHOCYTES)
-corona & germinal center contains B cells, FDCs, migrating dendritic cells; develop in response to an antigen |
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Term
Identify the histological characteristics, cell components, importance, disorders, functions of:
lymph nodes
-function?
-where are they most palpable, predominant
-the hilum
-the capsule
-reticular fibers (RF)
-the cortex
-fate of B cells
-medulla |
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Definition
ovoid/kidney-shaped, ENCAPSULATED
-lymph flows through, is filtered
-lymph is filtered at least once before returning to circulation
Human body has 500-700 lymph nodes
Palpable: submandibular, axillary, inguinal
most predominant in neck, axilla, inguinal, iliac vessels, aorta
HILUM: region where BV enter & exit and the efferent vessels exit
CAPSULE: surrounds lymph nodes
-dense irregular connective tissue
-deep subcapsular sinus receives AFFERENT LYMPHATICS
-TRABECULAE project from capsule into parenchyma of lymph node
RF hold lymph node cells in place
lymph nodes have a CORTEX & MEDULLA
lots of lymphoid sinuses are present in the medulla
CORTEX: has an outer dense mass of lymphoid cells
-outer cortex contains B cell-rich nodules
-inner cortex contains CD4+ T helper cells, which stimulate B cells to proliferate and differentiate; also has high-endothelial venules (HEV)
-activated B cells are attracted by FDCs that express complement factors CR1, CR2, CR3
Dying B cells with low affinity surface Ig are phagocytized by macrophages
B cells with high affinity Ig migrate to medullary cords and mature into PLASMA CELLS that secrete IgG or IgM that exits the lymph node
lies central to the cortex, extends to hilum
composed of medullary cords, reticular fibers, medullary sinuses
-medullary cords = partitions of reticular tissue from inner cortex; contain mainly B cells & plasma cells
activated B cells migrate from cortex as plasma cells, then enter medullary sinuses to secrete Ig
-medullary sinuses: transport lymph, lined by endothelial cells surrounded by reticular cells & macrophages |
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Term
Identify the histological characteristics, cell components, importance, disorders, functions of:
three tonsils |
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Definition
Palatine, pharyngeal, lingual
Encapsulated lymphoid nodules that are proactive (monitor entrance of foreign bodies)
found along the path of airborne & ingested antigens
react to antigens by forming lymphocytes, forming immune response
have a germinal center (site of B cell formation)
Palatine tonsils: b/t oral cavity & oropharynx; stratified squamous nonK epithelium
Pharyngeal: roof of nasopharynx; called adenoid when inflamed; pseudostratified ciliated columnar epithelium
Lingual: dorsal posterior surface of tongue, partially encapsulated; stratified squamous nonK epithelium; have lots of lymphoid nodules in parenchyma; have numerous mucous glands, each tonsil has a single crypt |
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Term
| The 2 primary components of lymphoid tissue |
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Definition
Reticular fibers: reticulin, type II collagen (not thymus)
Free cells: lymphocytes (helper T cells, cytoxic T cells, B cells); accessory cells (macrophages, antigen-presenting cells) |
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Term
| Describe the stromal compartment of the bone marrow |
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Definition
| A framework of ADIPOCYTES, FIBROBLASTS, MACROPHAGES, vascular ENDOTHELIAL CELLS, and blood vessels interspersed within TRABECULAR BONE |
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Term
| Describe the course of blood drainage in the bone marrow |
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Definition
| MEDULLARY SINUSES drain into the CENTRAL LONGITUDINAL VEIN and exit via the NUTRIENT VEIN |
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Term
B lymphocytes
-where do they originate?
-function?
-what can they turn into? |
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Definition
Originate from hematopoietic stem cells in the bone marrow, after which they mature
React to antigens in lymph nodes, spleen, etc. and differentiate into Ab-producing PLASMA CELLS
Responsible for HUMORAL IMMUNE RESPONSE, that's dependent on Ab formation
Activated B lymphocytes can become B MEMORY CELLS
-respond rapidly, to greater extent after second exposure to same ANTIGEN, can exist for ~50 yrs |
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Term
T lymphocytes
-where do they originate?
-function?
-where are they most abundant? |
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Definition
originate in the BM, migrate to CORTEX OF THYMUS to become IMMUNOCOMPETENT
CELL MEDIATED IMMUNE RESPONSE
respond to protein ANTIGENS, function at short distances
INNER CORTEX OF LYMPH NODES, PEYER'S PATCHES, PALS |
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Term
Antigen-presenting cells (APC)
-function?
-from what are they derived?
-examples?
-what do they produce & secrete? |
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Definition
phagocytize, catabilize, process antigens & present these antigens to T LYMPHOCYTES
derived from MONOCYTES
macrophages
dendritic cells (spleen, lymph node)
Langerhans' cells (stratum spinosum of epidermis)
activated B cells
thymic epithelial reticular cells
CYTOKINES inc INTERLEUKINS, TUMOR NECROSIS FACTORS, INTERFERONS |
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Term
CYTOKINES
-what are they?
-lymphokines
-monokines
-interleukins (IL-1 to IL-35) |
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Definition
Low-MW NON-AB PROTEINS secreted by MACROPHAGES & LEUKOCYTES in response to antigens
-act as INTERCELLULAR MEDIATORS in the immune response
-activate TARGET CELLS to perform their respective functions
cytokines produced by lymphocytes
produced by monocytes & macrophages
can activate and stimulate the proliferation and differentiation of leukocytes |
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Term
AIDS
-caused by?
-member of which family?
-what does HIV 1 infect? |
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Definition
caused by HIV 1
LENTIVIRUS family of RETROVIRUSES (long incubation period)
-lentivirus can deliver a lot of genetic material into the DNA of a host cell, one of the most efficient methods of a GENE DELIVERY VECTOR
*CD4* helper T cells, macrophages, dendritic cells, causing their destruction
-CD4 = glycoprotein surface R used by immune cells to exchange info
-HIV 1 can replicate in cells of lymph nodes for years before sx are detected |
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Term
AIDS
5 steps of how the virus infects & reproduces |
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Definition
1. RETROVIRUS binds & enters cell with its RNA and proteins
2. the VIRAL GENOME includes GAG (viral core proteins), POL (rtase), and ENV (components of viral coat)
3. RT converts vRNA -> DNA that's integrated into host DNA
4. PROVIRUS DNA directs synthesis of viral proteins & RNA
5. proteins enclose the vRNA to form VIRAL PARTICLES that bud from the cell |
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Term
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Definition
found in the inner cortex
have cuboidal epithelial lining
T cells & B cells use them to pass from blood into lymph node (DIAPEDESIS) |
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Term
| Flow of lymph in lymph node |
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Definition
| AFFERENT LYMPHATIC VESSELS, with valves, pierce the capsule, drain into SUBCAPSULAR SINUSES --> PARATRABECULAR (cortical) SINUSES --> cortex --> MEDULLARY SINUSES --> HILUM, form EFFERENT LYMPHATIC VESSELS |
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Term
| Blood supply to lymph node |
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Definition
Blood enter at hilum via 1-2 arterioles --> medullary branches --> capillary network corresponding to cortical lymphoid nodules & inner cortex
a SINGLE VEIN drains lymph node @ hilum |
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Term
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Definition
usually clonal B cells
neoplastic proliferation of lymphoid cells found in lymph nodes
large cells - multinucleated or bilobed nucleus
*dx of HODGKIN'S LYMPHOMA* |
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Term
| Normal cell size compared to lymphadenopathy |
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Definition
N: 10 mm
bacterial infxn: 1 in
pain can be caused by inflammation, or hemorrhage into the necrotic center of a malignant node
tenderness (+/-) doesn't differentiate b/t benign & malignant |
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