Chapter 16: Lymphatic System Flashcards
adaptive defense
resistance to particular pathogens or to their toxins/metabolic by-products
adaptive defense is…
3rd line of defense
antigens
non self molecules that can elicit an immune response
adaptive responses are carried out by __
lymphocytes & macrophages that can recognize specific antigens
2 types of adaptive defense
- cellular immune response
- humoral immune response
types of antigens (4)
- proteins
- polysaccharides
- glycolipids
- glycoproteins
T lymphocytes
- specialized in thymus
- make up 70-80% of circulating lymphocytes
- some settle in lymphatic organs (white pulp, lymph nodes, thoracic duct)
B lymphocytes
- released from bone marrow
- make up 20-30% of lymphocytes
- abundant in lymph nodes, spleen, bone marrow, intestinal lining
what does T cell activation require?
antigenic fragments to be attached to antigen presenting cell such as B cells, macrophages, etc
APC
antigen presenting cell; accessory cell
what does APC do to antigen?
phagocytizes antigen, digests it, & displays antigenic fragments on its own cell membrane, bound to protein that is part of the MHC or HLA
MHC
major histocompatibility complex
HLA
human leukocyte antigens
what happens when T cell encounters APC displaying antigenic fragments?
it can recognize antigen as foreign substance; T cell now activated
what can T cells secrete?
cytokines
cytokines
enhance some cellular responses to antigens
T cell types (3)
- helper
- cytotoxic
- memory
helper T cells
activate other cells; help B cells produce antibodies
cytotoxic T cells
attack virally infected/cancerous cells
memory T cells
provide future immune protection
types of cytokines (4)
- colony stimulating
- interferons
- interleukins
- tumor necrosis factor
colony stimulating cytokine
stimulate bone marrow to produce lymphocytes
interferon cytokine
block viral replication, stimulate macrophages, stimulate B cells to produce antibodies, attack cancer cells
interleukin cytokine
control lymphocyte differentiation & proliferation
tumor necrosis factor
stop tumor growth, releases growth factors, causes fever, stimulates lymphocyte differentiation
what must occur for B cells to respond?
proper cytokines are released from helper T cells; B cells respond by proliferating, enlarging clone of identical cells
what happens to B cells when they respond?
- some become memory B cells
- some differentiate into plasma cells, which produce & secrete larger globular proteins called antibodies
humoral/antibody-mediated immune response
antibodies are carried by the blood to infection site
what do both B cells & T cells require
proper activation; helper T cells secrete cytokines to activate B cells to proliferate
antibodies
- globular proteins
- also called immunoglobulins
- y shaped proteins; composed of 4 AA chains
- make up gamma globulin fraction of plasma proteins
5 major types of antibodies
- IgA (80%)
- IgG (13%)
- IgM (6%)
- IgE (<1%)
- IgD (<1%)
IgG
plasma and tissue fluid; defends against bacteria and activates complement
IgA
exocrine gland secretions; defends against bacteria and viruses
IgM
plasma; reacts with antigens on some red blood cell membranes following mismatched blood transfusions, and activates complement
IgD
surface of most B lymphocytes; B cell activation
IgE
exocrine gland secretions; promotes inflammation and allergic responses
