7. Adaptive Immunity Flashcards
Name 4 types of antigen-presenting cells and where they are found
Dendritic cells - lymph nodes
Langerhans’ cells - skin
Macrophages - most tissues
B cells - lymphoid tissue
What is macropinocytosis?
Engulfing of soluble particles, such as by antigen presenting cells
What type of immunity is activated by antigen presenting cells when they capture, process and present extracellular microbes? What does this involve?
Humoral immunity - B lymphocytes antibodies, complement, phagocytosis
What type of immunity is activated by antigen presenting cells when they capture, process and present intracellular microbes? What does this involve?
Cell-dependent immunity - cytotoxic T lymphocytes, antibodies, macrophages
What is the major histocompatibility complex (MHC)? What else can it be called?
Complex antigen presentation occurs by
HLA
What is the main function of MHC class I? Where are the class I molecules found?
Present peptides from intracellular microbes
All nucleated cells
What is the main function of MHC class II? Where are the class II molecules found?
Present peptides from extracellular microbes
Dendritic cell, macrophages, B cells
How does the genetics of MHC class I and II ensure that there is an increased number of different MHC molecules in an individual and also increased presentation of different antigens/microbes?
Co-dominant expression
Polymorphic genes
What are the two main structural features of MHC class I and II molecules?
Peptide binding cleft with highly polymorphic residues
Broad specificity
What type of T cells are MHC class I recognised by?
CD8+
What class of T cells are MHC class II recognised by?
CD4+
What MHC class does the endogenous pathway present antigens on? Which cells does this occur on?
MHC class I All cells with a nucleus
What MHC class does the exogenous pathway present antigens on? Which cells does this occur on?
MHC class II Antigen presenting cells
Which class of MHC molecules are HLA-A, HLA-B and HLA-C?
Class I
In both antigen presenting pathways what peptides are presented?
Both self and non-self
What does susceptibility to infections depend on?
Types of MHC molecule - if you have the right one to present the microbe
What can patients who are elite controllers or long-term nonprogressors do?
Control viral replication (high T cell count and low viral load)
What makes a HIV-infected individual a slow progress or?
HLA typing leads to
MHC molecules presenting key peptides for the survival of the virus (unmutated)
So effective T cell response
What makes a HIV-infected individual a rapid progressor?
Homozygote in HLA-1 alleles
MHC molecules presently mutated peptides (less critical for survival of virus)
Poor recognition by T cells, so poor T cell responses
What is the major cause for organ transplant rejection?
HLA molecules not a close enough match between donor and recipient. Can lead to graft-versus-host reaction
Name two autoimmune diseases that HLA molecules are thought to be associated with
Ankylosing spondylitis
Insulin-dependent diabetes mellitus
What is needed other than just the right receptors for the correct MHC and antigen, on a naive T cell for the activation of the cell?
Costimulatory signals
What class of MHC and therefore T cells activate cytotoxic T cells?
MHC class I and therefore CD8+ in the endogenous pathway (NB MHC class II will also be present) for intracellular microbes
What does the activation of cytotoxic T lymphocytes result in?
Infected cell death
