7.3 HOST-MICROORGANISM INTERACTIONS - IMMUNE RESPONSES Flashcards
→mechanism whereby the body is able to protect itself from invasion by disease causing organisms
Immunity
→consists of numerous cells and protein molecules that are responsible for recognizing and removing these foreign substances
Immune system
Immune system Divided into two broad categories
Innate or Natural immunity
Adaptive or Specific
little or no specificity immune system
Innate or Natural immunity
highly specialized immune system
Adaptive or Specific
Cells of the immune system
B Lymphocytes (B Cells)
T Lymphocytes (T Cells)
Natural Killer Cells (NK Cells)
B Lymphocytes (B Cells) Location
Lymphoid tissues (lymph nodes, spleen, gut- associated lymphoid tissue, tonsils)
B Lymphocytes (B Cells) Function
Antibody-producing cells
B Lymphocytes (B Cells) Subtypes
B lymphocytes
B-memory cells
Plasma cells
Cells waiting to be stimulated by an antigen
B lymphocytes
Activated B lymphocytes that secrete antibody in response to an antigen
Plasma cells
Long-lived cells preprogrammed to antigen for subsequent exposure
B-memory cells
T Lymphocytes (T Cells) Location
Circulate and reside in lymphoid tissues (lymph nodes, spleen, gut-associated lymphoid tissue, tonsils)
T Lymphocytes (T Cells) Subtypes:
Helper T cells
Cytotoxic T cells
Suppressor T cells
Interact with B cells to facilitate antibody production
Helper T cells
Recognize and destroy host cells that have been invaded by microorganisms
Cytotoxic T cells
Mediate regulatory responses within the immune system
Suppressor T cells
Similar to that of cytotoxic T cells; however do not require the presence of an antigen to stimulate function
Natural Killer Cells
Immediate response to the pathogen that does not confer long lasting protective immunity
INNATE, OR NATURAL,
NONSPECIFIC IMMUNITY
INNATE, OR NATURAL,
NONSPECIFIC IMMUNITY examples
Physical and chemical barriers
Blood proteins
phagocytosis
Blood proteins that act as
mediators of infection
Cytokines,
Complement
→capable of being specific for distinct molecules, responding in particular ways to different types of foreign substances and developing memory, which allows for a more vigorous response to repeated exposures to the same foreign invader
ADAPTIVE, OR SPECIFIC IMMUNITY
2 types of ADAPTIVE, OR SPECIFIC IMMUNITY
Humoral or Cellular Immune Response
major constituents of the adaptive or specific immune response
Lymphocytes and Antibodies
able to remember each time it encounters a particular foreign antigen
Immunologic Memory
→Antibody mediated
. HUMORAL IMMUNE RESPONSE
Immunoglobulin G (IgG) percent of the total serum immunoglobulin pool
→70% to 75%
Immunoglobulin G (IgG) halflife in serum
3 to 4 weeks
→cross the maternal placenta to the
fetus
→ passive immunity for newborns,
neutralization of viruses and exotoxin;
responds best to protein antigens, mainly involved in secondary (anamnestic) immune response
Immunoglobulin G (IgG)
→ cannot cross the placenta
→consists of five basic subunits—each composed of two heavy chains and two light chains (similar to an IgG molecule) and linked to another polypeptide chain (J chain) by disulfide bonds
→endotoxin neutralization, bacterial agglutination, complementmediated bacteriolysis, strong opsonization ability; responds best to polysaccharide antigens, mainly involved in primary immune response
Immunoglobulin M (IgM)
Immunoglobulin M (IgM) percent of igms
10-15
Immunoglobulin M (IgM) half-life in serum
5 days
→predominant immunoglobulin class in certain body secretions, such as saliva, tears, and intestinal secretions
→ prevention of bacterial and viral invasion of mucous membranes through interference with adherence of
microorganism to site; found in tears, milk, saliva, and respiratory and GI secretions
Immunoglobulin A (IgA)
Immunoglobulin A (IgA) percent
15% to 20%
IgA occurs when
two subunits (each similar to an IgG molecule) linked together by a J chain
contains a secretory component that stabilizes the molecule
Secretory IgA
→increase during infection by numerous parasites and may play a
role in eliminating these infectious agents from the host
→major role in allergic response
Immunoglobulin E (IgE)
→little is known; may serve as a B-cell receptor or play a role in autoallergic diseases
Immunoglobulin D (IgD)
relatively rapid appearance of IgM antibodies
Primary immune response
Antibody Responses
Primary and Secondary
→rapid increase in IgG antibody associated with higher levels, a prolonged elevation, and a more
gradual decline
Secondary or Anamnestic immune response
→based on the action of specific kinds of T-lymphocytes that directly attack the cells that are infected with virus, parasites, cancer cells or transplanted cells
CELL-MEDIATED IMMUNE RESPONSE
→ primary effector cell in cell-mediated immunity
T Lymphocyte
→low-molecular-weight proteins resulting from antigen binding, activation, cell division, and differentiation of the T cell
Lymphokines
Mechanisms by Which Microbes May Overcome Host Defenses
a. Bringing about tolerance
b. Immunosuppression
c. Change in the appropriate target for the immune response
d. Antigenic variation
inability to induce an immune response to a microbial antigen
Tolerance
Antigenic variation example
Borrelia recurrentis
