Histo Immune System & Lymphoid Organs

innate immune system

a component of the immune system that is composed of generalized and non-specific defenses and/or responses to pathogens and has no immunological memory; acts fast

adaptive immune system

has immunological memory, specificity, diversity, and the ability to distinguish self from non-self

T lymphocytes

adaptive immune system cells that are responsible for cell-mediated immune responses; assist in developing humoral responses to thymic-dependent antigens

humoral response

The branch of acquired immunity that involves the activation of B cells and that leads to the production of antibodies, which defend against bacteria and viruses in body fluids.

T lymphocytes, B lymphocytes, and antigen-presenting cells

What are the 3 cells of the adaptive immune system?

innate immune system

Toll-like receptors, mast cells, eosinophils, neutrophils, macrophages, and NK cells are all part of which immune system component?

cytokines

In the adaptive immune system, T lymphocytes, B lymphocytes, and APCs communicate with each other by the use of signaling molecules called _____________.

toll-like receptors (TLRs)

a family of at least 14 receptors that can be located in the cytosol of specific innate immune system cells or as integral proteins in their cell membranes; recognize bacterial components once paired

TRC4-TRC4

What TLR pair recognizes lipopolysaccharides of gram-negative bacteria?

TRC2-TRC6

What TLR pair recognizes peptidoglycan of gram-positive bacteria and zymosan of fungi?

TNF-alpha, interleukin 12

Once toll-like receptors bind to their ligand, they cause the release of _____________, ______________, and other cytokines.

clone

a small number of identical cells that can recognize and respond to a single or small group of related antigenic determinants

epitopes

the part of an antigen molecule to which an antibody attaches itself and that stimulates immune responses

T-cell receptors

___________ are present on the surface of T lymphocytes and recognize only protein antigens

protein antigens

What kind(s) of antigens do TCRs recognize?

MHC (major histocompatibility complex)

T lymphocytes recognize only epitopes that are bound to ________________ molecules on the surface of APCs.

thymus

Where does T cell maturation occur?

immunoincompetent

What word describes T cells before they migrate from the bone marrow to the thymus?

thymic cortex

Within the ______ ______, thymocytes undergo gene rearrangements and begin to express antigen-specific TCRs.

-outside of the lymphatic nodules in MALT

-paracortex of lymph nodes

-PALS of the spleen

What are the T-cell regions in secondary lymphoid organs?

lymphoblasts

Pro-T lymphocytes develop into _________ in the thymus.

helper T cells, cytotoxic T cells, regulatory (supressor) T cells

What are the 3 types of T-lymphocytes?

CD4 T cells

T-lymphocytes that are able to recognize and react with antigens presented by cells associated with MHC II

CD8 T cells

T-lymphocytes that are able to recognize and react with antigens presented by cells associated with MHC I

Class I molecules (MHC I)

Which MHC molecules are expressed by nearly all nucleated cells?

Class II molecules (MHC II)

Which MHC molecules are expressed by the various cells that function as APCs?

CD4

What is the surface marker for helper T cells?

CD8

What is the surface marker for cytotoxic T cells?

CD4

What is the surface marker for regulatory (suppressor) T cells?

MHC II

which MHC class is associated with CD4 T cells?

MHC I

Which MHC class is associated with CD8 T cells?

helper T cells

Which type of T-lymphocytes help promote antibody production, stimulate proliferation of eosinophils and mast cells, and indirectly promote and activate other immune cells?

cytotoxic T cells

Which type of T-lymphocytes directly kill target cells (virus-infected cells, tumor cells, and transplanted cells/grafts)?

regulatory (suppressor) T cells

Which type of T-lymphocytes suppress the humoral and cellular immune responses and are involved with immunological tolerance?

cellular immune response

What immune response involves the destruction of infected cells by cytotoxic T cells, or the destruction of intracellular pathogens by macrophages? (doesn't involve antibodies)

plasma cells and memory B cells

What are the 2 types of active B cells?

plasma cells

Which active B cells produce antibodies and participate in the humoral immune response?

memory B cells

Which active B cells have a long life (months to decades) and are capable of differentiating into plasma cells?

IgG

the most abundant type of immunoglobin

IgG

type of immunoglobin that is able to cross the placenta, is a major Ig during the 2nd immune response, and has a high antigen binding specificity

IgA

type of immunoglobin that is the major type in external secretions (milk, saliva, tears, sweat, and mucus) of epithelial and gland epithelium cells; protects mucosal surfaces

IgM

type of immunoglobin that is the principal Ig in the primary immune response; activates macrophages and serves as an antigen receptor on the B cell surfaces

IgE

type of immunoglobin that is found only in a small amount in blood serum; binds to Fc receptors of the mast cells and basophils and plays important role in allergic reactions

IgD

type of immunoglobin that is found in low concentrations in blood serum; serves along with IgM as an antigen receptor on the membranes of mature B cells

immunoglobulins

• Ig molecules on B-lymphocyte surface membranes mediate antigen recognition

• plasma cells secrete antibodies after B-cell activation

B-lymphocytes

lymphocytes that function by differentiating into antibody-secreting plasma cells and reside in lymphoid nodules

lymphoid nodules

Where do B-lymphocytes reside?

B-lymphocytes

Which type of lymphocytes are associated with the humoral immune response?

T-lymphocytes

lymphocytes that function by differentiating into helper T cells, cytotoxic T cells, and regulatory T cells and reside in T-cell regions

T-lymphocytes

Which type of lymphocytes are associated with the cell-mediated immune response?

T-cell receptor (TCR) and CD4 and CD8 markers

What is antigen recognition mediated by in the surface membranes of T-lymphocytes?

bone marrow, thymus, mucosa-associated lymphoid tissue (MALT), lymph nodes, spleen

List the lymphoid organs

bone marrow and thymus

What are the primary lymphoid organs?

bone marrow

What primary lymphoid organ is associated with B lymphocytes?

MALT, lymph nodes, spleen

What are the secondary lymphoid organs?

HIV

What infection is associated with a decline in CD4+ helper T cells and loss of cell-mediated immunity?

CD4+ helper T cells

What type of cells are affected by HIV/AIDS?

true

T/F: No B cells or lymphatic nodules are present in the thymus.

lymphatic nodules

small, localized clusters of dense tissue formed by lymphocytes and macrophages

Hassall corpuscles

structures in the thymic medulla formed by Type VI epithelial reticular cells with keratinization; increase with age

epithelial reticular cells

cells in the thymus that surround lymphocytes in the cortex, form Hassall corpuscles in the medulla, and maintain the blood-thymus barrier in the cortex

immunocompetent

Thymocytes undergo gene rearrangement and become ___________ thymocytes within the cortex.

effective or memory T cells

What do thymocytes become after migrating from the thymic medulla to the secondary organs?

thymosin, serum thymic factors, and thymopoietin hormone

What 3 things do epithelial reticular cells produce?

blood-thymus barrier

What prevents foreign antigens from entering the thymus?

immunocompetent naive T cells, macrophages, and type V and VI epithelial reticular cels

What cell types are found in the medulla of the thymus?

GALT, BALT, and tonsils

What are the components of the MALT (mucosa-associated lymphoid tissue)?

palatine, pharyngeal, lingual

3 types of tonsils

primary lymphatic nodules

lymphatic nodules that contain mostly small (inactive) B cells and don't have a germinal center

secondary lymphatic nodules

lymphatic nodules that contain mostly large (active) B cells and have a germinal center

appendicitis

common disease involving bacterial and viral infection, hyperplasia of lymphatic nodules, and abdominal pain

lymphatic nodules

What structure(s) in the appendix does appendicitis affect?

M (microfold) cells

specialized cells with short apical folds and no microvilli that transfer foreign antigens to lymphocytes in Peyer's patches; harbor T and B cells and dendritic cells; have a large intracellular pocket at the basal surface

palatine tonsil

one of a pair of almond-shaped masses of lymphatic tissue in the posterolateral walls of the oral cavity, lined by stratified squamous epithelium; has deep, branched crypts and mostly lymphatic nodules

non-keratinized stratified squamous epithelium

What type of epithelium lines the palatine tonsils?

pharyngeal tonsil

epithelial invagination in the posterior roof of the nasopharynx, lined by pseudostratified columnar epithelium; mostly diffuse lymphoid tissue and some lymphatic nodules

pseudostratified columnar epithelium

What type of epithelium lines the pharyngeal tonsil?

B; T

______ cells are located in the cortex of lymph nodes, and _____ cells are located in the paracortex.

medullary cords

___________ ________ in lymph nodes extend inward from cortex and contain B cells, T cells, and plasma cells.

medullary sinuses

___________ _________ in lymph nodes communicate with efferent lymphatics and contain reticular cells and macrophages.

afferent lymphatic vessel

What carries lymph from the peripheral tissues into the lymph node?

efferent lymphatic vessel

Vessel in which lymph and lymphocytes leave a lymph node en route to the blood

HEVs (high endothelial venules)

the site where most lymphocytes enter the lymph node from the blood; specialized post-capillary veins with receptors for antigen-primed lymphocytes; lined by cuboidal cells and contain rich glycoproteins that attract lectinlike receptors

diapedesis

the passage of blood cells through the intact walls of the capillaries, typically accompanying inflammation; HEVs are a major site for this

spleen

HEVs are located in all secondary lymphoid organs except which one?

L selectin

lectin-like receptors expressed in leukocytes, attracted by the glycoproteins in HEVs

paracortex

Where are HEVs located in lymph nodes?

germinal center of lymphatic nodule

What structure is the arrow on the left of the image pointing to?

lymph node

What part of the immune system is this?

Hodgkin lymphoma

malignant lymphoid cancer that causes enlargement of lymph nodes, fever, night sweats, weight loss, and fatigue; associated with Reed-Sternberg cells

Reed-Sternberg cells

cells associated with Hodgkin lymphoma

white pulp

What part of the spleen contains lymphatic nodules (B cells), a central artery, a periarterial lymphatic sheath (T cells), and an immune component?

red pulp

What part of the spleen contains splenic (Billroth) cords and splenic sinuses, filters antigens, engulfs aged erythrocytes, and is a reservoir for erythrocytes and platelets?

erythrocytes and platelets

The red pulp in the spleen is a reservoir for _______ and __________.

PALS (periarterial lymphatic sheath)

What is the T-cell area of the spleen?

sinusoid

Enlarged capillary that serves as a blood channel; located in red pulp of spleen

GALT (gut associated lymphoid tissue)

What is lymphoid tissue called in the gut?

Peyer's patches

large example of GALT in the ileum

geminal center

Name the structure in the ileum.

mantle

Name the structure in the ileum.