Adaptive Immunity Flashcards
What is SCID?
severe combined immunodeficiency –> when you dont have an adaptive immune system
what are 4 features of adaptive/specific immunity?
- specialized immune cells
- specific responses
- self/non-self recognition
- memory generation (remembering the antigen)
what is the specificity of the adaptive immune system based on?
antigen recognition
what is an antigen?
- most are proteins
- foreign molecules recognized by adaptive immune cells
- elicit an immune response
how long does it take for adaptive immunity to develop?
5-7 days roughly
what is adaptive immunity mediated by?
B lymphocytes (humeral / blood) --> humeral is body fluids, blood and lymph T lymphocytes (cell-mediated)
what are b-lymphocytes?
b-lymphocytes produces antibodies in response to specific antigens to fight infection
they produce cytokines, chemical signals that change behaviour of other cells
act as APCs (antigen presenting cells) –> activates other immune cells to combat infection
where are b-lymphocytes produced and mature?
in the bone marrow – this is antigen independent
where are b-lymphocytes activated?
in the peripheral lymphoid organs (i.e. lymph nodes)
this is antigen dependant (reacts and activates to antigens)
where are b-lymphocytes differentiated?
- differentiation occurs after they recognize antigen
- they differentiate into plasma or memory B cells
in the lymph nodes (peripheral lymphoid organs)
this is also antigen decedent because they produce specific antibodies to a specific antigen
what is the process of b-cell activation and differentiation in 4 steps?
- antigen binds to IBM antibody which causes signalling
- COLONIAL EXPANSION: clones of b-cell with same antibody get produced (rapid cell division and proliferation)
- a portion of those clones become Memory cells and are stored for second encounter of antigen
- the majority of the clones become plasma cells or effector cells which secrete antibodies
what are the two commonalities between the proliferating b-cells during colonial expansion?
they have the same:
- B cell receptor (BCR)
- specificity for antigen
which two antigens does b-cell activation dependent on?
- Thymus-dependent (TD) antigens –> proteins like bacterial cell wall components or parts of capsule [requires t-helper cell contact to help with memory]
- Thymus-independent (TI) antigens –> mostly other molecules like sugars and carbs
cytokines
cytokines are solvable proteins secreted by immune cells
they are chemical signals that can change the behaviour of other cells
can cause b-cell proliferation (clonal expansion) and class switching
class switching
changing ig (antibody) produced by B cell (i.e. IgM to gig) with no loss of antigen specificity
production of different antibodies depending on the cytokine environment around plasma cells and depends on infection
what are the two regions of the antibody?
Fab region –> where the antigen binds [Y shaped arms]
Fc region -> constant region which is recognized by other immune cells that have a Fc receptor (used by phagocytes to find the pathogen after the antibody binds to it)
5 functions of antibodies
- opsonization
- complement activation (activation of MAC)
- agglutination
- neutralization
- antibody-dependent cell-mediated cytotoxicity
How do antibodies preform opsonization?
antibodies recognize bacterial antigens and the FAB region binds them
then macrophages have Fc receptor that bind the antibody Fc stem which in turn eats the antigen-antibody complex
how do antibodies activate the complement pathway?
antibodies that attach to the antigen attract the C3b complement protein which is an opsonin –> then that activates the entire complement pathway forming MAC (membrane attack complex) and cell lysis
how do antibodies cause agglutination?
each Y shape arm of the antibody can bind to an antigen and then form a ring and clump together; this attracts the phagocytes and allows them to take up more pathogens at once