Adaptive Immunity Flashcards
Where are APC’s found?
skin- SALT
mucous membranes- GALT, NALT, BALT, GUALT
lymphoid organs- lymph nodes, spleen
blood circulation- plasmacytoid/myeloid DC’s
What do dendritic cells present to?
found in lymph nodes, blood, mucous membranes. present to naive t cells
What do langerhans cells present to?
found in skin, present to naive t cells
What do macrophages present to?
found in various tissues, present to effector t cells
What do B cells present to?
found in lymphoid tissues, present to effector t cells and naive t cells
How do extracellular and intracellular PAMPs provoke differing responses?
extracellular PAMPs- mainly bacteria- recognised by APCs- cause humeral immunity (antibodies, complement, phagocytosis)
intracellular PAMPs- mainly viruses- recognised by APCs- cause cell dependent immunity (cytotoxic t cells, t lymphocytes, antibodies, macrophages)
What are MHC molecules?
class 1 found on all nucleated cells (HBA1, HBA2, HBA3). main function is for intracellular microbes.
class 2 found on dendritic cells, macrophages, b cells. main function is for extracellular microbes.
note they have codominant expression so numbers and types of mhc molecule vary between individuals.
MHC class I recognized by CD8+ T cells MHC class II recognized by CD4+ T cells
How do HLA types link to HIV?
slow progressors have HLA-B27 HLA-B51 HLA-B57. MHC molecules present key peptides for the survival of the virus (unmated). Effective T cell response produced.
rapid progressors have HLA-B35 and are Homozygotes in HLA-I alleles. MHC molecules present mutated peptides (less critical peptides for the virus). Poor recognition by T cells and poor T cell responses.
What are some clinical problems with MHC molecules?
Major causes for organ transplant rejection:
- HLA molecules mismatch between donor and
recipient (Allograft)
- Graft-Versus-Host reaction (GVH)
• HLA association and autoimmune disease
- Ankylosing spondylitis= HLA-B27 in 90% of patients
Insulin-Dependent Diabetes Mellitus= HLADQ2 in 50-75% of patients
Describe the different ways extracellular and intracellular microbes are processed
extracellular microbes recognised by mhc class 2 proteins on APC, which activates CD4+ T cells which provokes a humeral response.
in the case of intracellular microbes, there is cross presentation. apc’s use mhc class 1 and class 2 to present to CD8+ and CD4+ T cells. this is because cd4+ t cells are necessary to produce cytotoxic t cells.
mhc cells present to TCR’s. note that there are costimulatory signals which means that cytokines are produced which enhance the interaction between tcr’s and mhc’s.
naive t cells can become different types of t cells.
Explain how the right T helper cells are stimulated by T helper cells
extracellular microbes provoke production of th2 and th17 type t cells.
intracellular microbes production of th1 type t cells. this is important as they are required for APC’s to be able to activate cytotoxic t cells. the cytotoxic cells can then target virally infected cells which express the viral peptides (all nucleated cells have class 1).
cd4+/th1 also sends signals to b cells to produce antibodies.
cd4+/th2 can send signals to activate eosinophils/mast cells also.
cd4+/th17 activates neutrophils.
How does antibody response differ on different encounters to a pathogen?
On 1st encounter rates of IgG: IgM are low
On 2nd encounter rates of IgG:IgM high.
IgM levels are constant but IgG increases on second encounter. (faster production and longer duration)
offers immunity
Describe the immune functions of different antibodies
IgG: Fc-dependent phagocytosis, Complement activation, Neonatal Immunity, Toxin/virus neutralization
IgE: Immunity against helminths, Mast cell degranulation (allergies)
IgA Mucosal Immunity
IgM Complement activation
