- present fragments of endocytosed foreign proteins (antigens) to lymphocytes via MHC II - mostly derived from monocytes (I.e. macrophages)

- act as target to allow elimination of abnormal host cells - present peptide fragments (“normal self”) to cytotoxic CD8+ T lymphocytes

- presents partially digested endocytosed foreign peptides (“non-self”) to helper CD4+ T lymphocytes - critical in immune interactions

Lymphatic (immune) system Flashcards by Lindsay Kirkpatrick

Lymphatic system

Group of cells, tissues & organs that monitor the body & react to presence of potentially harmful substances & infectious agents

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Lymphocytes

Definitive cell type & the effector cells in the immune system response
(Primary functional cell of immune system)

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Primary lymphatic organs

Bone marrow
Thymus

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Secondary lymphatic organs

Lymph nodes
Spleen
Diffuse & mucosal-associated lymphatic tissue (MALT)

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2 branches of immune system

Innate immunity (natural, nonspecific)
Adaptive immunity (acquired, specific)

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Mediating cells of innate immunity

Phagocytic cells:
neutrophils, macrophages/monocytes, NK cells

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Adaptive immunity involves ____ & ____ activation against ____ antigens

B & T lymphocytes
Specific

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adaptive immunity

Antigens are presented to lymphocytes by phagocytic ____

Antigen presenting cells (APCs)

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Antigen

Any substance that can induce a specific immune response

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APCs

present fragments of endocytosed foreign proteins (antigens) to lymphocytes via MHC II
mostly derived from monocytes (I.e. macrophages)

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adaptive immunity

2 types of specific defences

Humoral immunity
Cell-mediated immunity

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Humoral immunity

Production of antibodies (immunoglobulins) by B lymphocytes which have differentiated into plasma cells

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Cell-mediated immunity

Response to transformed & infected cells for destruction by specific killer cells (involves T lymphocytes)

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Epitopes (antigenic determinants)

Small molecular domains of the antigen immune cells can recognize & react to major histocompatibility complex (MHC)

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MHC molecules are produced by…

supergene located on chromosome 6 in humans

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MHC 1 expressed on surface of….

All nucleated cells & platelets

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MHC 1 functions

act as target to allow elimination of abnormal host cells
present peptide fragments (“normal self”) to cytotoxic CD8+ T lymphocytes

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different types of cells in lymphatic & hematopoietic tissue are identified by ____ on their surface

Cluster of differentiation (CD) markers

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Human version of MHC

human leukocyte antigen (HLA)

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MHC II is expressed on the surface of ____

all APCs

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MHC II functions

presents partially digested endocytosed foreign peptides (“non-self”) to helper CD4+ T lymphocytes
critical in immune interactions

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how are CD molecules designated?

designated by numbers according to an international system that relate them to antigens expressed on their surfaces at different stages in their differentiation

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T lymphocytes are differentiated in the ____ but produced in the ____

thymus
bone marrow

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T lymphocytes are involved in ____

cell-mediated immunity

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T lymphocytes recognize antigenic epitopes via surface protein complexes called ____

T-cell receptors (TCRs)

T lymphocytes only recognize antigens when presented as part of ____

MHC molecules

3 subsets of T lymphocytes

1. helper T lymphocytes (CD4) 2. cytotoxic T lymphocytes (killer T cells/CD8) 3. regulatory (suppressor) T lymphocytes

Helper T lymphocytes express ____

CD4+ markers (=CD4+ T cells)

TCRs and CD4 bind ____

MHC II (“non-self”) molecules

what happens when CD4 binds MHC II?

- activate cytotoxic CD8+ T cells - activate macrophages to become phagocytic & produce cytokines - activate NK cells - promote differentiation of B cells to plasma cells

Cytotoxic T lymphocytes (Killer T cells) express ____

CD8 markers (= CD8+ T cells)

TCRs with CD8 bind ____

MHC I (normal self) molecules

regulatory (suppressor) T lymphocytes express ____

CD4+ and CD25+

function of regulatory (suppressor) T lymphocytes

inhibit excessive immune responses (inhibit other immune cells)

B lymphocytes differentiate in ____

bone marrow

B lymphocytes are involved in ____

humoral immunity

B lymphocytes are covered with many ____, which bind ____

B-cell receptors (BCRs) Foreign antigens

B-cell receptors are monomers of ____ or ____

IgM or IgD (antibodies/immmunoglobulins)

B cells mature into ____

plasma cells and memory B cells

function of plasma cells

produce antibodies against specific antigen that was originally bound and processed

memory B cells

long lived, allows rapid response upon subsequent exposure to antigen

what allows for a faster response to subsequent exposure to an antigen?

memory B cells (activation of B lymphocytes produces clones of memory B cells)

basic structure of an antibody

2 light chains + 2 heavy chains forms an antibody molecule (monomer)

function of variable portion (Fab) of antibody

bind antigen (at a specific epitope)

function of constant region (Fc) of antibody

bind to surface receptors of cells

Name the 5 major classes of antibodies

(GAMED) 1. IgG 2. IgA (secretory IgA) 3. IgM 4. IgE 5. IgD

what is the most abundant class of antibody?

IgG

functions of IgG

- passive immunity in fetus/newborn (^soluble, cross placenta) - opsonization (brings antibody to cell with receptor for it)

which antibody type is present in most secretions?

IgA (secretory IgA)

what is the largest type of antibody?

IgM

when is IgM produced?

mainly produced in **initial response** to antigen

IgE has Fc receptors on ____

basophils & mast cells

when IgE binds to its cells, it triggers ____

allergic reaction

IgD is bound to ____ and acts as ____

surface of B lymphocytes antigen receptors (BCR)

actions of antibodies

1. compliment activation 2. opsonization 3. NK cell activation

what is compliment activation?

- compliment system = group of ~20 plasma proteins - when activated, cascade of enzymatic reactions result in **rupture (lyse) of cell membranes** invading cells

what is opsonization?

- receptors on macrophages, neutrophils, & eosinophils recognize Fc receptors of antibodies attached to microorganism - facilitates **phagocytosis** by leukocytes

NK cell activation

- antibodies bound to antigens on virus-infected cells recognized by NK cells - NK cells release proteins (perforin & granzymes) -> cause death of infected cell

what are NK cells?

specialized to kill certain types of target cells

What happens when TCRs & CD8 bind MHC I?

CD8 cells attached to transformed cells release chemicals causing apoptosis

B cells bound to foreign antigens present ____ on their surface

MHC II

B cells present antigens expressed as MHC II to ____

CD4 T helper cells