B cells Flashcards
(27 cards)
B Cell Outline
Contains a B cell receptor (BCRs). Recognoise peptide, carbohydrate and lipid antigens independent of other cells. On activation secretes IL-2 so B cell undergoes colonial expansion and differentiates into different plasma cells. Secretes antibodies into plasma and mucus
Different names for antibodies
antibody = immunoglobulin = Ig
Differences between T and B cells
T cells only recognise peptide antigens on MHCs + B cells recognise specific antigens in all forms, B cells produce antibodies and T cells produce cytokines. T cells develop in thymus (in brain) and B cells develop in bone marrow
BCR Outline
Antibody as a membrane receptor that recognises specific antigen in all forms. Same structure as antibodies secreted into blood stream. IgM. 2 heavy and 2 light chains held together by disulfide bonds. Contains 2 regions: variable (receptor binding) and constant
Primary (Generative) Lymph Organs
Bone Marrow and Thymus (brain)
Secondary (Peripheral) Lymph Organs
Lymph node, spleen and mucosal and cutaneous lymphoid tissue
How do B cells produce multiple antigens
VDJ gene rearrangement
Receptors on Immature B Cells
IgM, membrane bound antigen receptor
Receptors on Mature B Cells
IgM and IgD are co-expressed. IgD receptors are introduced in spleen. Mature B cells circulate blood, lymph and spleen looking for antigen
B cell development steps
BCR presence (positive selection) and self selection (negative)
BCR presence Outline
B cells are positively selected when they express a full BCR
B cells negative selection
Have to bind loosely to self antigens
2 stimulatory signals for t cells
BCR antigen binding and Helper T cell activation
BCR Antigen Binding Reaction
specific antigen binds to BCR. B cell phagocytoses antigen, enters endolysosome and is places on MHC 2 receptor on cell’s surface.
Helper T cell activation signal
After Helper T cell is activated by MHC2 on B cells. T cell sends signal CD40L receptor which binds to CD40 on B cells. B cells produce cytokines for T cell differentiation also drive B cell proliferation and differntiation
Epitopes Def
Specific region on antigen binding site complimentary in shape to specific antigen
Antibody Structural Features
Recognises antigens and binds tightly, complement binding Site and Immune cell binding site
Antigen Binding Site Outline
Binds sterically specific antigens. At 2 tips of antibodies at ends of light and heavy chains
Complement binding site
On base of antibody (heavy chain). C1q protein binds there to start complement cascasde
Immune Cell Binding Site Outline
On base of antibody below complement binding site. contains Fc receptors that immune cells to increase antibody functionality
What does B cell activation result in
Antibody production, Isotype switching, affinity maturation and memory cell formation
Isotype Switching Outline
Converting IgMs into other isoforms of antibody dependent of infection requirements. Antigen binding site (variable regions) remains the same but heavy chain (constant region) switches. Induced by CD40-CD40L interaction. Each isotope has a different function
IgG Outline
Monomer (1 variable + 1 constant region). Neutralises microbes, oponisation, complement activation and NK attractant (cytoyoxic). Can cross placenta
Ig A
Dimer (2 variable regions + 2 constant). Neutralises pathogens. Produced at mucosal membranes
