Immune System pt 1 Flashcards
what are the functions of the immune system
- recognize and eliminate pathogenic agents
- disposing cells and debris (mutant cells to limit)
- wound healing
describe the 3 components of the immune system
- physical barriers
- leukocytes
- lymphoid tissues
briefly describe physical barriers
- skin (cells packed together tightly)
- mucous membranes (continuous barrier to skin)
describe the various layers of the skin and how they help with immunity
- epidermis has tightly packed epithelial cells
- dermis is thick connective tissue
- provide good physical protection unless pierced
where can we find mucous membranes and what is their purpose
- nose, mouth, anus, vagina make viscous mucous to block particles
- GI tract and stomach make acids to kill microorganisms
- next level of defense if skin not applicable
what are the types of leukocytes
- neutrophils
- eosinophil
- basophil
- monocyte
- lymphocyte
these are WBCs
what are the categories of leukocytes
- granulocytes (BENG)
- agranulocytes (LAM)
- based on presence of granules in cytoplasm
how do leukocytes derive
hemopoietic/hematopoietic stem cells in bone marrow
describe granulocytes
- have cytoplasmic granules
- contain secretory products
- release thru degranulation
describe phagocytes
- engulf foreign particles and microorganisms and remove them from blood or tissues
- neutrophils, eosinophils, monocytes (eat MEN) -> blood
- macrophages, dendritic cells (DM) -> tissues
what are the cells that mature in tissues
macrophages, mast cells, dendritic cells
describe macrophages
cells that derive from monocytes
describe mast cells; where are they found, what do they secrete
- cells forming in bone marrow from hematopoietic stem cells
- found in mucous membranes
- secrete histamine
describe dendritic cells
- cells forming in bone marrow from hematopoietic stem cells
- activate certain T-cells
- EX phagocytose pathogens
what are the roles of lymphocytes
to provide:
- diversity
- specificity
- memory
- ability to distinguish self from non-self in immune system
what are the main types of lymphocytes
- B cells
- T cells
- null cells (most natural killer = NK)
describe B cells, what is their speed
- flag antigens (targets) with antibodies
- intermediate speed
draw the pathway of B cell interacting with antigen
B cell contacts antigen so it differentiates into a plasma cell which then secrete antibodies (immunoglobins) that attach onto foreign invader
describe T cells
- direct attackers to foreign or abnormal cells (infected, mutant, transplanted)
- slowest speed
draw pathway of T cell interacting with infected cells
T cell contacts infected cells and after days it turns into a cytotoxic T cell which secretes molecules that make pores in the target cell’s membrane which causes the cell to fill with fluid which causes cell to rupture
describe NK cells
- small proportion of circulating lymphocytes
- crucial for fighting viral infections
- kill virus-infected cells which limits new virus production
- use similar mechanism to T cells but recognize infected cells differently
- fastest response
what are the 2 types of lymphoid tissues
central (primary) and peripheral (secondary)
describe central/primary tissues
- lymphocytes made and mature here
- bone marrow, thymus, fetal liver
describe cell development in bone marrow
- leukocytes and RBCs
- T cells migrate to thymus for maturation
- B and T cells migrate to peripheral tissues after maturity
describe peripheral/secondary tissues
- collections of B & T cells, macrophages
- spleen, lymph nodes, tonsils, adenoids, appendix, lymph nodules in GI, Peyer’s patches in small intestine
what pathogens activate immune response
virus, bacterium, fungi, parasites
describe bacteria as a pathogen
- gram + and - categories
- can infect in different ways (stick and release toxins, endo- and exo- toxins)
describe viruses as a pathogen
- only takes small amt time to start extreme cascade
describe parasites as a pathogen
- go thru life cycles very quickly
- typically spread by vectors (flies, mosquitos, food w/ eggs)
- each generation will make a new protein to be one step ahead of your immune system which allows it to continue living
- EX tapeworms, hookworms, trypanozoans
describe fungi as a pathogen
- immune system is responding to spores
- mycoses diseases caused by them
draw out the layers of defense
barriers -> non-specific immune response -> specific immune response -> pathogen destruction/suppression
describe barriers as a layer of defense
- physical and chemical (enzymes, antibodies, pH)
describe non-specific immune response
- rapid, non-specific, no memory
- WBCs
- chemicals (complement system, interferons)
describe specific (adaptive) immune response
- slow, specific, memory
- cell-mediated responses (B; T cytotoxic, helper, regulatory)
- antibody-mediated responses (antibodies)
what are some types of nonspecific defenses
- physical barriers
- inflammation
- interferons
- complement system
how do nonspecific defenses distinguish self from non-self
- distinguish self from non-self via pathogen associate molecular patterns (PAMPs)
- proteins associated w/ nonspecific defense act as pattern recognition receptors and bind PAMPs
describe inflammation as a defense mechanism
series of events that cause accumulation of proteins, fluid, and phagocytes in an injured or invaded area
draw the flow to steps of inflammation
- macrophages engulf debris and foreign matter
- capillaries dilate and become more permeable
- foreign matter is contained
- more leukocytes migrate to area
- leukocytes clear infection
describe the phagocytosis stage of inflammation
- macrophages detect bacteria thru receptors
- cytokine proteins important for cell signaling (autocrine, paracrine)
describe the dilation of capillaries stage of inflammation
- blood flow increases due to histamine dilating capillaries
- the more histamine releases, the more dilation that happens to a point
- fluid, leukocytes, defensive proteins release to tissues
describe the containment stage of inflammation
- mast cells and basophils release heparin
- heparin prevents clot formations initially so that leukocytes can access the area first
- the clot formed will have the pathogen
describe the leukocyte migration/proliferation stage of inflammation
- cytokines trigger movement of leukocytes
- neutrophil migration takes 1 hr
- monocyte migration to macrophages takes 10 hrs
- leukocytosis
what are the steps of movement that cytokine triggers for leukocytes
- margination
- attachment
- diapedesis
- chemotaxis
describe the clearing of infection stage of inflammation
- neutrophils and macrophages clear the tissue thru phagocytosis and secretion of cytokines
describe chemotaxis
- cytokines get into tissue and gain ability to recognize bacteria by secretion of chemicals (interleukin 8)
what are the steps to phagocytosis
- attachment
- internalization
- degradation
- exocytosis
describe the attachment stage of phagocytosis
- the substance that should be engulfed is recognized either by shape or pattern recognition receptors
- opsonins are on surface of engulfing cell (small molecules)
describe the internalization stage of phagocytosis
- takes ~0.01s
- phagosome and lysosome combine to make a secondary lysosome
describe the degradation stage of phagocytosis
the lysosome enzymes degrade the phagocytosed product
describe the exocytosis stage of phagocytosis
some degradation products are eliminated
describe interferons as a defense mechanism
- prevention of virus spread in body
- interferes with viral replication
- proteins are secreted by leukocytes and virus infected cells make interferon α and interferon β
describe interferon γ
- secreted from active T cells and NK cells
- inhibits viral replication
- enhances phagocytosis by macrophages
- boosts antibody production in B cells
- helps activate NK cells and cytotoxic T cells
- inhibits cell division (defense from cancer and cancerous cells)
describe a complement system
- 30 plasma proteins resulting in mechanisms to kill invading microorganisms esp bacteria
- can act (non)specifically depending on whether antibodies are present
- can be activated using 3 pathways
what are the pathways that can activate the complement system
classical, lectin, alternative
what are the results of complement activation
opsonization, leukocyte recruitment, histamine secretion, MAC
describe the classical pathway
- depends on presence of antibodies (involving proteins C1-C9)
- slow
- antigen and antibody make c1 complex -> c2b and c4b fragments make c3 convertase -> c3 then hydrolyzes (leading into alternative)
describe the alternative pathway
- nonspecific
- intermediate speed
- doesn’t rely on production of antibodies
- activates at point further along than classical (C3)
- c3 hydrolyses into fragments -> C5 cleaved by c3b fragment -> c5b to c9 make cylindrical complex that bursts cell
describe the lectin pathway
- nonspecific
- fastest
- doesn’t rely on production of antibodies
- lectins bind specific carbs
- MBL + mannose -> MASP -> C2 and C4 proteins
describe MAC
- membrane attack complex
- nonspecific
- first complement protein attaches to bacterial cell -> cascade of protein activation slope on membrane -> MAC forms on pore
- swelling of cell leads to lysis
describe natural killer cells
- early operation in nonspecific defense
- recognize abnormal/infected cells
- lysis of pathogen occurs thru secretion of perforins
- can attack virus-infected cells w/out identifying virus
- defense against viral infections, tumors, bacteria, and protozoans
- part of specific immune response
