Exam 2 (Lecture 12) - T Helpers, B and T Interactions Flashcards
List the different types of lymphocytes and how they recognize antigen.
Types of Lymphocytes:
1) Large granular lymphocytes
- NK cell (can sometimes be seen on light microscopy)
- Gamma-delta T cells (not in the body very much)
2) Cytotoxicity T Cells (CTLs)
How they recognize antigens:
1) B cells; B cell receptors; unprocessed intact antigens
(recognize protein, lipids and CHO, etc)
2) T Helper; TCR + CD4 molecule bind MHC II + its
peptide (antigen that’s specific); also has CD3
3) Cytotoxicity T cell; TCR + CD8 molecule to bind MHC 1 +
its peptide (antigen that’s specific); also have CD3
List the effector function, including signature cytokine(s) of TH1, TH2, TH17, Treg, and TFH.
ALL T cells have a TCR and CD4 molecule and CD3 molecule.
T helper cells help by secreting cytokines; they’re a different subtype because they secrete different cytokines.
- TH1 = interferon gamma (signature cytokine) that activates
M1 macrophage; for diseases like intravesicular pathogens
(Viral and bacterial infections); extracellular infections IgG - TH2 = IL-4 and IL-13 activate eosinophils and mast cells; for parasitic infections and allergic responses; IgE class-switching
- TH-17 = IL-17; activate and recruit neutrophils; for bacterial and fungal infections
- Treg = TFG-beta (immunosuppressive); to prevent autoimmunity
- TFH = IL-21; secrete cytokines in the lymphoid tissue (follicle; B-cell rich); cause class-switching in B cells (cause them to make something other than IgM); have TH1 and TH2 cytokine profiles.
Explain how an immune response to one type of pathogen can inhibit the response to a different kind of pathogen and give an example of a clinical situation where this may play a role.
Interferon gamma can inhibit IL-4; if a puppy has parasites they have a TH2 environment; you would want to vaccinate with a vaccine that’s going to active the TH1 response.
Describe what you could do to get T cell help to B cells when B cells are responding to a polysaccharide antigen (like a bacterial capsule). Remember, a TH cell recognizes a peptide in an MHC II molecule.
B cell receptors bind to polysaccharides, but T cells would not respond b/c there is no peptide (you need T cell cytokines to get the B cells to undergo mitosis and class-switch); so, you could bind the polysaccharide covalently to a protein/peptide.
List 3 significant signals required to get activation of a naive T helper cell and two significant factors that determine the subtype of TH cell that predominates in a response.
Activation of a naive T cell:
1) A peptide presented on MHC II
- TCR + CD4+ —> CD3 signals)
2) Cytokines
3) Co-stimulatory molecules
Factors that could determine which T helper:
1) The type of infection (parasite, viral, bacterial)
2) The environment (mucosal surface, lymph node, etc)
Use your understanding of immunologic response to describe the generally expected response to a modified-live vaccine and an inactivated (killed) vaccine.
Modified Live:
- Virus is modified in a way that they don’t cause disease;
but they can infect cells.
- Get B cell response, T helper cells (via endogenous/
exogenous pathways to get CTL activation as well
Killed Vaccine:
- Virus maintains epitopes but cannot infect cells
- B cells respond; a BCR binds to an epitope on the
antigen
- DC can phagocytose the antigen, process it through
exogenous pathway and present it on MHC II to CD4+
(T helper)
- This protects the animal by producing IgG antibodies
(high titer of IgG)
If you did a biopsy of a lump from a bovine TB test with a light microscope, what would the predominant cell type be?
Memory T lymphocytes and some monocytes
- mononuclear cell infiltrate = monocytes/macrophages
Explain how the predominant cells leave the bloodstream, including the initiating event and important molecules involved. (FYI - when the tuberculin is injected, there is a local inflammatory response).
Upregulation of addressins, so molecules of memory cells are exiting out.
Antigen presenting cells are presenting antigen on MHC II and the memory cells recognized it and responded.
The gamma interferon test for bovine TB is a blood test. The mononuclear cells from a whole blood sample are isolated from a cow. What are the two different types of mononuclear cells identifiable with a light microscope in the bloodstream?
1) Monocytes
2) Lymphocytes
When the tuberculin is added to these cells, a measurable amount of gamma interferon is produced if the cow is infected with the organism. In a cow that is not infected, there is not a measurable amount of gamma interferon produced.
What cell type is producing the majority of the gamma interferon?
T Helper 1
Based on what you know about B and T cell recognition of antigen, what type of immune response would you expect from the polysaccharide alone vaccine?
B cells (IgM antibody); No T cell response
What type of immune response would you expect following the conjugate vaccine?
B cells and T helper cells (CD4+; high titer IgG)
What is the reason for the differences in the responses?
B cells recognize the polysaccharide and T cells recognize the diphtheria toxoid (protein/peptide molecule)
