Lymphatic (immune) system Flashcards
Lymphatic system
Group of cells, tissues & organs that monitor the body & react to presence of potentially harmful substances & infectious agents
Lymphocytes
Definitive cell type & the effector cells in the immune system response
(Primary functional cell of immune system)
Primary lymphatic organs
Bone marrow
Thymus
Secondary lymphatic organs
Lymph nodes
Spleen
Diffuse & mucosal-associated lymphatic tissue (MALT)
2 branches of immune system
- Innate immunity (natural, nonspecific)
- Adaptive immunity (acquired, specific)
Mediating cells of innate immunity
Phagocytic cells:
neutrophils, macrophages/monocytes, NK cells
Adaptive immunity involves ____ & ____ activation against ____ antigens
B & T lymphocytes
Specific
adaptive immunity
Antigens are presented to lymphocytes by phagocytic ____
Antigen presenting cells (APCs)
Antigen
Any substance that can induce a specific immune response
APCs
- present fragments of endocytosed foreign proteins (antigens) to lymphocytes via MHC II
- mostly derived from monocytes (I.e. macrophages)
adaptive immunity
2 types of specific defences
Humoral immunity
Cell-mediated immunity
Humoral immunity
Production of antibodies (immunoglobulins) by B lymphocytes which have differentiated into plasma cells
Cell-mediated immunity
Response to transformed & infected cells for destruction by specific killer cells (involves T lymphocytes)
Epitopes (antigenic determinants)
Small molecular domains of the antigen immune cells can recognize & react to major histocompatibility complex (MHC)
MHC molecules are produced by…
supergene located on chromosome 6 in humans
MHC 1 expressed on surface of….
All nucleated cells & platelets
MHC 1 functions
- act as target to allow elimination of abnormal host cells
- present peptide fragments (“normal self”) to cytotoxic CD8+ T lymphocytes
different types of cells in lymphatic & hematopoietic tissue are identified by ____ on their surface
Cluster of differentiation (CD) markers
Human version of MHC
human leukocyte antigen (HLA)
MHC II is expressed on the surface of ____
all APCs
MHC II functions
- presents partially digested endocytosed foreign peptides (“non-self”) to helper CD4+ T lymphocytes
- critical in immune interactions
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
T lymphocytes are differentiated in the ____ but produced in the ____
thymus
bone marrow
T lymphocytes are involved in ____
cell-mediated immunity
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
- helper T lymphocytes (CD4)
- cytotoxic T lymphocytes (killer T cells/CD8)
- 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
- compliment activation
- opsonization
- 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
