CD4 T-Cells: Master Controllers of Immune System Flashcards
T cells develop in the ____
T cells develop in the thymus
which cells are progressively lost in HIV infection
CD4+ T helper cells are progressively lost in HIV infection
which immune cells are the main cells to turn into antigen presenting cells (APCs)
Professional APCs include dendritic cells (DCs), monocytes, macrophages, and B cells, whereas all other cell types that express MHC I molecules are considered non-professional APCs
what is the function of cytotoxic T cells
cytotoxic T cells (CD8+) directly kill intracellular pathogens and eliminate mutated and cancerous cells. These immune responses are generated by T-cells when they recognize an antigen, which is exposed to them by antigen-presenting cells.
n.b. The CD8+ receptor on a cytotoxic T-cell can only bind to MHC-1
what is the function of activated CD4+ T helper cells?
T helper cells provide help by making cytokines!! They differentiate (into ‘different flavours’) and they control the type of resulting immune response: this can be cell-mediated immunity (intracellular pathogens) or humoral immunity (extracellular pathogens)
E.g. an activated CD4+ T cell decides to become a CD4+ Th1 Cell= these produce cytokines, particularly, IFN-gamma(activated natural killer cells, macrophages) + TNF-alpha N.B. THIS IS CELL MEDIATED IMMUNITY (i.e. concerns intracellular pathogens)
If an activated CD4+ T cell decides to become a CD4+ Th2 Cell= these produce interleukins e.g. IL-4 (activate mast cells, eosinophils, basophils and prime potent antibody responses from B cells like class switching IgE), IL-5, IL-13= THIS IS HUMORAL IMMUNITY (i.e.concerns extracellular pathogen)
what kind of immune cells do Th1 cells help?
Th1 cells help macrophages
n.b. we don’t activate macrophages unless we absolutely need to because they are hyperresponsive, classically activated macrophages can cause tissue damage, whereas overactive macrophages involved in wound healing can promote fibrosis and exacerbate cytotoxic and allergic responses
what kind of immune cells do Th2 cells help?
Th2 cells help B cell make antibodies
which cytokine is a T cell growth factor
Cytokine IL-2
(IL-2 is critical for the development of T regulator cells aka Tregs in the thymus and the regulation, proliferation, and maintenance of Tregs in peripheral tissues, and is essential for maintaining the transcriptional program required for Treg function.)
What are the 5 types of antibodies and their function?
IgA= Found in saliva, tears, mucus, breast milk and intestinal fluid, IgA protects against ingested and inhaled pathogens.
IgD= found on the surface of B cells. Though its exact function is unclear, experts think that IgD supports B cell maturation and activation.
IgE= Found mainly in your skin, lungs and mucus membranes, IgE antibodies cause your mast cells to release histamine and other chemicals into bloodstream. IgE antibodies can cause allergic reactions.
IgG= most common antibody, making up approximately 70% to 75% of all immunoglobulins in your body. It’s found mainly in blood and tissue fluids. IgG antibodies help protect your body from viral and bacterial infections.
IgM= found in your blood and lymph system, IgM antibodies act as the first line of defense against infections. They also play a large role in immune regulation.
Th0 cells (undifferentiated CD4+ cells) differentiate into a CD4+ Th2 cell because of which cytokine?
Mast cells (innate immune cell) make IL-4, IL-4 stimulates the production of an undifferentiated aka CD4+ Th0 cell into a CD4+ Th2 cell
Th0 cells (undifferentiated CD4+ cells) differentiate into a CD4+ Th1 cell because of which cytokines?
Th0 cells differentiate into Th1 cells in the presence of IL-12/IL-23
what is the function of IL-12
IL-12 =interleukin, its a heterodimeric cytokine
IL-12; it’s role is the activation of T cells and NK cells, leading to an increased production of IFN-γ, proliferation, and cytotoxic potential. IL-12 also induces the production of TNF-α, IL-2, IL-3, IL-8, and IL-10, while stimulating the proliferation of hematopoietic precursors and B cells.
IL-12 is produced by antigen-presenting cells and plays a critical role in host defense against intracellular microbial infection and control of malignancy via its ability to stimulate both innate and adaptive immune effector cells.
what is the function of IL-4
IL-4 has an important role in regulating antibody production, hematopoiesis and inflammation, and the development of effector T-cell responses. It is produced only by a subset of activated hematopoietic cells, including T cells and Fc epsilon R1+ mast cells and basophils.
2 manifestations of leprosy exist:
* Tuberculoid leprosy - limited disease
* Lepromatous leprosy - disseminated disease
which differentiated CD4+ T cell is dominant in this response
**Tuberculoid leprosy - limited disease ** (this is the response that will keep u alive)=
* Th1 dominant response
* Cytokines - INF-gamma
* Activated macrophages
Low no. organisms
**Lepromatous leprosy - disseminated disease **=
* Th2 dominant response ( this will kill u)
* Cytokines - IL-4/5/13
* Hyperglobulinaemia - overproduction of more than 1 class of antibody by plasma cells
*High no. organisms
What are the 2 responses to tuberculosis by differentiated CD4+ cells
- Lepromatous tuberculosis ak latent TB (asymptomatic/mild symptoms)
=body responds with Th1 dominant (create lots of IFN-gamma stimulating macrophages and keeping u alive)
*limb deformity and loss of sensation cuz overactivated macrophaes (leper colonies cuz they survived)
*milliary TB (can be fatal, patient v ill; this TB can spread to brain + spinal cord)
=body responds with Th2 dominant (create loads of IL-4= inadequate response bacteria proliferate quickly and patient dies soon)
