Lymphoid Histology I/II (W2)

What is the main purpose of the immune system?

protect against invading organisms (infection)

Commensal organisms are defined as ______.

organisms that inhabit the host without causing disease

The microbiota refers to ______.

organisms found in a specific location

The microbiome includes ______.

microbiota plus their environment and secretions

Commensal organisms contribute to host health by ______.

producing vitamin K, competing with pathogens, aiding digestion

Pathogenic organisms are defined as ______.

organisms that cause disease

Opportunistic pathogens cause disease when ______.

immunity is decreased or barriers are compromised

The four major pathogen categories are ______.

bacteria, viruses, fungi, parasites

Intracellular pathogens require ______ for elimination.

killing of infected cells

Extracellular pathogens are susceptible to ______.

soluble effector molecules

Antigens are defined as ______.

molecules recognized by immune cells that trigger response

The three categories of barriers to infection are ______.

mechanical, chemical, microbiological

Mechanical barriers include ______.

epithelial junctions, stratum corneum, cilia

Chemical barriers include ______.

mucus, sebum, antimicrobial peptides, acidic environments

Microbiological barriers include ______.

commensal organisms

The immune system consists of ______.

cells, tissues, organs

The immune system must distinguish between ______.

self and non-self

Immunology is defined as ______.

study of mechanisms defending against harmful organisms

Specialized immune structures include ______.

cells, tissues/organs, microenvironment

Innate immune cells include ______.

granulocytes, macrophages, dendritic cells, NK cells

Granulocytes include ______.

neutrophils, eosinophils, basophils, mast cells

Adaptive immune cells include ______.

B cells and T cells

B cells differentiate into ______.

plasma cells that secrete antibodies

T cells mediate ______ immunity.

cellular

Microenvironment refers to ______.

supportive environment enhancing immune cell activity

Endosteal niche contains ______.

stromal cells, osteoblasts

Perivascular niche contains ______.

cells secreting cytokines (macrophages, endothelial cells)

Pathogen recognition involves ______.

host receptors interacting with pathogens

Recognition is performed by ______.

cell surface receptors and soluble proteins

Innate immunity is ______.

genetically preprogrammed and rapid

Innate response occurs within ______.

hours to days

Innate immune recognition is ______.

non-specific

Innate effector mechanisms include ______.

macrophages, neutrophils, NK cells, complement, cytokines

Innate response has two phases ______.

immediate and induced

Adaptive immunity is ______.

specific and changes with exposure

Adaptive immunity is mediated by ______.

lymphocytes (B and T cells)

Adaptive response is ______ compared to innate.

slower

B cell receptors are ______.

immunoglobulins

T cell receptors require ______.

MHC antigen presentation

Epitope is defined as ______.

specific region of antigen recognized

APCs include ______.

macrophages, dendritic cells, B cells

Primary lymphoid organs are where ______.

lymphocytes develop

Primary lymphoid organs include ______.

bone marrow and thymus

Secondary lymphoid organs are where ______.

lymphocytes encounter antigens

Secondary lymphoid organs include ______.

lymph nodes, spleen, MALT

Tertiary lymphoid tissue forms during ______.

chronic inflammation

General histologic features of lymphoid tissue include ______.

reticular CT, lymphocytes, APCs, plasma cells

Lymphocytes have ______ nuclei and ______ cytoplasm.

basophilic; minimal

Bone marrow is located in ______.

medullary cavities of bones

Bone marrow types are ______.

red and yellow marrow

Red marrow contains ______.

hematopoietic cells

Yellow marrow contains ______.

adipocytes

Red marrow structure includes ______.

reticular CT, hemopoietic cords, sinusoids

Sinusoids have ______ endothelium.

discontinuous

Red marrow function includes ______.

RBC, WBC, platelet production

Macrophages in marrow perform ______.

recycling of iron from old RBCs

Yellow marrow increases with ______.

age

The thymus is located in ______.

superior mediastinum above heart

The thymus is ______ shaped.

bilobed

Thymus contains ______.

capsule, septa, incomplete lobules

Each thymic lobule has ______.

cortex and medulla

Thymus is largest ______.

before puberty

Thymus undergoes ______ after puberty.

involution

Cortex contains ______.

cortical thymic epithelial cells (cTECs)

cTECs form ______.

blood-thymus barrier

Blood-thymus barrier prevents ______.

antigen exposure to thymocytes

Stellate TECs form ______.

cytoreticulum

Stellate TECs function as ______.

APCs and cytokine producers

Corticomedullary barrier is formed by ______.

squamous TECs

Medulla contains ______.

medullary TECs (mTECs)

mTECs form ______.

cytoreticulum and boundary layers

Hassall corpuscles ______.

secrete cytokines

Mature T cells exit via ______.

venules and efferent lymphatics

T cell maturation involves ______.

genetic recombination and receptor expression

Helper T cells express ______.

CD4

Cytotoxic T cells express ______.

CD8

CTLs kill via ______.

perforin and granzymes

Central tolerance occurs via ______.

selection processes

Positive selection occurs in ______.

cortex

Negative selection occurs in ______.

medulla

The spleen is located in ______.

left upper quadrant

Spleen is surrounded by ______.

dense CT capsule

Trabeculae carry ______.

vessels and nerves

Splenic pulp consists of ______.

red pulp and white pulp

White pulp contains ______.

lymphoid nodules and PALS

Red pulp contains ______.

sinusoids and splenic cords

Stave cells line ______.

sinusoids

Splenic microvasculature includes ______.

arteries → arterioles → capillaries

Closed circulation means ______.

blood remains in vessels

Open circulation means ______.

blood enters splenic cords

Spleen functions include ______.

filter blood, remove RBCs, immune response

Lymph nodes are ______ shaped.

bean-shaped

Lymph nodes are located ______.

along lymphatic vessels

Afferent lymphatics enter at ______.

convex surface

Efferent lymphatics exit at ______.

hilum (concave surface)

Lymph node regions are ______.

cortex, paracortex, medulla

Cortex contains ______.

B cell nodules

Paracortex contains ______.

T cells and HEVs

HEVs allow ______.

lymphocyte entry from blood

Medulla contains ______.

medullary cords and sinuses