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
What is antibody titer?
relative amount of antibody in the serum
- reflects intensity of humoral response
What is naturally acquired active immunity?
antigens enter the body naturally
- body induces antibodies and specialized lymphocytes
What does naturally acquired active immunity result from?
infection
What is naturally acquired passive immunity?
antibodies pass from mother to fetus through the placenta or to infant through the mother’s milk
What is artifically acquired active immunity?
antigens are introduced in vaccines
- body produces antibodies and specialized lymphocytes
What are artificially acquired passive immunity?
preformed antibodies in immune serum are introduced by injection
