Lecture 12 Flashcards
What happens during cellular immunity?
- produces T lymphocytes to recognize antigenic peptides processed by phagocytic cells
What are T cell receptors?
on the T cell surface to contact antigens
- causes the T cells to secrete cytokines instead of antibodies
What happens during cellular immunity?
attacks antigens that have already entered cells
- like viruses
What happens during humoral immunity?
fights invaders and threats outside cells
- extracellular bacteria and toxins
- viruses before they enter a host cell
How do T cells combat intracellular pathogens?
- thymic selection eliminates immature T cells
- migrate from the thymus to lymphoid tissues
- attach to antigens via t-cell receptors
Where are T cells mature?
thymus
What is the cellular immunity response process?
pathogens enter the gastrointestinal tract and pass through microfold cells (M cells) in Peyer’s patches
- transfers antigens to lymphocytes and antigen-presenting cells (APCs)
What are examples of antigen-presenting cells? (APCs)
- dendritic cells
- macrophages
Where are dendritic cells found? What is their function?
- found in skin, genital tract, lymph nodes, spleen, thymus, blood
- engulfs and degrades microbes and display them to T cells
What is the function of macrophages? How are they activated?
- migrate to lymph tissue to present antigen to T cells
- activated by cytokines or the ingestion of antigenic material
What are the 2 clusters of differentiation? What’s in them? What do they do?
- CD4+ = T helper cells that bind MHC class II molecules on B cells and APCs
= cytokine signaling with B cells; interact directly with antigens - CD8+ = cytotoxic T lymphocytes that bind MHC class I molecules
How do T helper cells work?
t-cell receptor on the cell recognize and bind to the antigen fragment and MHC class II on antigen-producing cell
- secretes costimulatory molecule to activate T helper cell
What does the T helper cell produce?
cytokines
What do the cytokines differentiate into?
- T helper 1 cells
- T helper 2 cells
- T helper 17 cells
- memory cells
What do T helper 17 cells produce? What does it lead to?
IL-17
- contributes to inflammation
What do T helper 1 cells produce? What does it lead to?
IFN-gamma
- activates macrophages
- enhances complement
- stimulates antibody production that promotes phagocytosis
What do T helper 2 cells produce? What does it lead to?
IL-4 cytokine
- activates B cells to produce IgE
- activates eosinophils
What are T regulatory cells?
- subset of CD4+ cells
- carry additional CD25 molecule
What is the function of T regulatory cells?
suppresses T cells against self
- protects intestinal bacteria required for digestion
- protects fetus
How do cytotoxic T lymphocytes formed? How do they work?
precursor T cytotoxic cells are activated to become cytotoxic T lymphocytes (CTLs) with the help of T-helper cell and costimulatory signals
- CTLs recognize and kill self-cells altered by infection (self-cells carry endogenous antigens on MHC class I molecules)
- CTLs release perforin and granzymes that induce apoptosis in the infected cell
Why does apoptosis happen?
- prevents the spread of infectious viruses into other cells
- cells cut their genome into fragments, causing the membranes to bulge outward via blebbing
What is the function of natural killer cells?
- granular leukocytes destroy cells that don’t express MHC class I self-antigens
- kill virus-infected and tumor cells and attack parasites
- not always stimulated by an antigen
- form pores in the target cell, leading to lysis or apoptosis
What happens to protozoans and helminths since they’re too big to be pahgocytized?
- target cell is coated with antibodies
- immune system cells attach to Fc regions of antibodies
- target cell is lysed by chemicals secreted by the immune system cell
What happens during the secondary response after the second exposure to an antigen?
- class switching where initial IgM response shifts to IgG, IgE, IgA
- memory cell produced in response to the initial exposure are now activated by the secondary exposure
