chapter 18: immune system

Describe the process of phagocytosis.

"Once neutrophils and other leukocytes arrive at the site of an infection, they begin the process of destroying invading pathogens by phagocytosis. The initial step in phagocytosis is contact between the surfaces of the phagocyte and pathogen. One of the major triggers for phagocytosis during this contact is the interaction of phagocyte surface receptors with certain carbohydrates or lipids in the pathogen or microbial cell walls." "Contact is not always sufficient to trigger engulfment, however, particularly with bacteria that are surrounded by a thick, gelatinous capsule. Instead, chemical factors produced by the body can bind the phagocyte tightly to the pathogen and thereby enhance phagocytosis."

Describe the sequence of events that leads to cytotoxic T-cell activation. Identify the targets of cytotoxic T cells and how these targets are killed.

a cytotoxic T cell binds via its membrane to cells bearing a viral antigen or cancer associated antigen in association with a class 1 MHC protein activation of the cytotoxic T cell also requires a cytokine secreted by helper T cells, themselves activated by antigen presented by a macrophage. the cytotoxic T cell then releases perforin, which kills the attached target cell by making leaky

Define briefly the function of Toll-like receptors.

evolutionary ancient proteins that recognize pathogen associated molecular patterns that are highly conserved features of pathogens. TLR's belong to a family of proteins called pattern-recognition receptors and may be among the first molecules to have evolved in eukaryotic organisms to combat microbial diseases

Apply the role of MHC's to T cells: cytotoxic T-cell receptors and helper T-cell receptors.

helper T cells- class II, found only in macrophages, dendritic cells, and B cells Cytotoxic T cells: class I, found on all nucleated cells of the body

essential cells in adaptive immune responses

lymphocytes are the essential cells -- activated B cells -- activated cytotoxic T cells -- plasma cells

Differentiate between active and passive immunity.

passive: direct transfer of antibodies from one person to another, the recipient thereby receiving preformed antibodies - a mother to a fetus or baby bc antibodies pass in the placenta and breast milk - injections given to a patient suffering from certain infections active: resistance to infection due to contact w microorganisms and toxins or antigens

name the major anatomical and biochemical barriers to infection

- anatomical: inherited general defense - biochemical: cells change throughout lifetime to combat pathogens the body's first lines of defense against microbes are the barriers offered by surfaces exposed to the external environment and their various glands that secrete antimicrobials various skin glands, salivary glands, and lacrimal(tear) glands have a more active function in immunity by secreting antimicrobial chemicals this may include antibodies, enzymes such as lysozyme, which destroys bacterial cell walls; and an iron binding protein called lactoferrin EX: along GI tract and respiratory tract cough and sneeze reflex and the hairs in your nostrils provide a defense too

List the names and general functions of the major types of cells that mediate immune defenses.

- leukocytes: white blood cells -- serve as recognition cells in adaptive immune responses and are essential for all aspects of these responses -- neutrophils, monocytes, macrophages, and dendritic cells have a variety of activities, but particularly important is their ability to secrete inflammatory mediators and to function as phagocytes. - luekocytes are split in to two groups: myeloid and lymphoid cells 1. myeloid cells include: neutrophils, basophild, eosinophils and monocytes 2. lymphoid: B lymphocytes(B cells), lymphocytes(t cells), natural killer cells and plasma cells macrophages: found in virtually all organs and tissues, their structures varying somewhat from location to location and they are derived from monocytes that pass through the walls of blood vessels to enter tissues and transform into macrophages. they are strategically placed where they will encounter their targets dendritic cells: populations of myeloid-derived cells that are not macrophages but exert macrophage like functions such as phagocytosis - extensions from their plasma membrane at certain stages of their life cycle - highly motile and are found scattered in almost all tissues but particularly at sites where the internal and external environments meet, such as a digestive tract Mast cells: found throughout connective tissues, particularly beneath the epithelial surfaces of the body and are derived from the differentiation of a unique set of bone marrow myeloid cells that have entered the blood and then left the blood vessels to enter connective tissue, where they differentiate and undergo cell division.

Differentiate between innate immune responses and adaptive immune responses.

-innate immune responses defend against foreign substances or cells without having to recognize their specific identities -- known as NONspecific immune responses - adaptive immune responses depend upon specific recognition by lymphocytes of the substance or cell to be attacked -- known as specific immune responses

Describe the three stages of adaptive immune responses

1. a lymphocyte programmed to recognize a specific antigen and encounters it and binds it via plasma membrane receptors specific for the antigen 2. the lymphocyte undergoes activation- a cycle of cell divisions and differentiation 3. the multiple active lymphocytes produced in the manner launch an attack all over the body against all specific antigens that stimulated their production

Describe the sequence of events that constitutes the innate inflammatory response after you have a wound and entry of pathogen/foreign particle.

1. bacteria are introduced into the would 2. chemical mediators cause vasodilation and capillary permeability; chemoattractants recruit neutrophils to area 3. diapedesis results in neutrophils entering tissue where they engulf bacteria 4. capillaries return to normal as neutrophils continue to clear the infection

define cytokines and explain why they are of importance

the cells of the immune system secrete a multitude of protein messengers that regulate host cell division(mitosis) and function in both innate and adaptive immune responses and they link the components of the immune system together and are the chemical communication network that allows different immune systems to "talk" to one another.

Describe the differences between B-cells, T-cells and NK cells.

B cells: mature in the bone marrow and are carried to the secondary lymphoid organs, where additional B cells arise by cell division NK cells: originate in the bone marrow T cell precursors leave the bone marrow, migrate to the thymus, and undergo maturation there. These cells then circulate between the blood and secondary lymphoid organs. stimulation w antigen and costimulatory molecule lead to T cells expansion by cell divison.

identify the names and functions of the primary and secondary lymphoid organs

the primary sites of maturation of lymphocytes that will then be carried to the secondary lymphoid organs, lymph, blood, and all the body's organs and tissues primary: bone marrow and thymus secondary: lymph nodes, spleen, tonsils, and lymphocyte collections in the linings of the body's tracts

Describe the antiviral roles of type I and type II interferons.

type I: stimulate cells to produce antiviral proteins(innate response) Type II: stimulate proliferation and secretion of cytotoxic compounds

Explain the role of chemotaxis in the immune response.

with the onset of inflammation, circulating neutrophils begin to move out of the blood across the endothelium of capillaries and venuels to enter the inflamed area