Body Defenses Flashcards
What are the main activities of the immune system?
- defend against pathogens
- remove worn-out cells or tissue damaged by trauma or disease
- destroy abnormal cancer cells
Define Bacteria
non-nucleated, unicellular organisms; contain all nuclear machinery necessary for survival and reproduction
Define viruses
nucleic acids (DNA or RNA) enclosed by a protein coat; are not organisms and cannot self sustain
- invade host cell and hijacks resources toward viral replication
What does virulence mean?
disease caused by pathogenic bacteria usually due to their release of enzymes or toxins that injure or disrupt normal cell function
Which are phagocytes?
leukocytes (neutrophils and monocytes) with the ability to engulf and destroy foreign particles
What are the two types of lymphocytes?
B cells and T cells
Define B cells
produce antibodies that indirectly lead to destruction of foreign material
Define T cells
lymphocytes that directly destroy virus invaded cells and cancer cells
Where are leukocytes produced?
bone marrow
Where are lymphocytes produced (after development)?
lymphoid tissues– spleen, thymus, bone marrow, tonsils, adenoids
What does the spleen do?
clears blood of microorganisms, debris, and worn-out blood cells; exchanges lymphocytes with blood
What are the two components of the immune system? What cells mediate them?
Innate immune system (neutrophils and macrophages)
Adaptive immune system (B cells and T cells)
How does the immune system detect these triggers?
Toll-Like Receptors, RLRs, and NLRs,
What are the four defenses of the innate immune system?
Inflammation, Interferon, Natural Killer cells, and the complement system.
What paracrine do macrophages and helper T cells release?
cytokines
What does histamine do?
paracrine that vasodilates nearby arterioles
What is diapedesis?
cytokines cause other leukocytes inside capillaries to adhere to capillary wall and squeeze through capillary pores
What is scar tissue made of?
deposits of collagen protein
When is interferon released? What does it do?
when cells are infected by a virus, interferes with ability of virus to replicate in other potential host cells.
What do natural killer cells do?
lymphocyte-like cells that nonspecifically destroy virus-infected cells and cancer cells.
What is the complement system?
plasma proteins work together to attack the plasma membrane of foreign cells. Contains many sequentially activated plasma proteins that circulate in blood stream in inactive form.
What is the protein complex it creates that leads to the destruction of microbes? How do these microbes end up dying from it?
membrane attack complex (MAC)
What is the difference between the alternate and classical complement pathways?
Alternate: first component (C1) activated directly by carbohydrate chains protruding from plasma membrane of foreign microbes
Classical: First component (C1) activated by antibodies, which are attached to foreign material– part of the adaptive immune system
B-cell receptors are specific for ________.
one type of antigen
What is an antigen?
large molecule (usually protein, also large carbs or fats) that triggers immune response in the body
What is the difference between T-dependent and T-independent antigens?
T-dependent antigens depend on assistance of helper T cells to activate B cell while T-independent antigens directly activate B cell with no assistance.
What happens when a B cell is activated?
multiplies and its clones differentiate into active plasma cells or dormant memory cells
What are the ways in which an attached antibody leads to the destruction of the microbe/host cell carrying an antigen?
- triggering the complement system (classical complement pathway)
- binds with phagocyte to promote phagocytosis
- activated antibodies bind with receptors on natural killer cells to trigger lysis
What is a way in which an antibody renders an antigen useless
antibodies bind with antigens on multiple foreign bodies, forming a useless clump (agglutination)
What is clonal selection theory?
the enormous array of B cells with different B-cell receptors is established during fetal development before exposure to antigens
What specifically leads to the diversity of B cell receptors?
During B-cell development, the fragments of DNA encoding B-cell receptors are cut, reshuffled, and splized in many combination cross developing B cells
What leads to a greater response to secondary exposure to an antigen?
Memory cells
How does vaccination lead to a secondary response when exposed to an antigen?
by deliberately exposing to a pathogen stripped of its disease producing capabilities in order to form memory cells to the pathogen.
What is cell-mediated immunity? How is it different than antibody-mediated immunity?
T-cells attack targets via direct contact. while in antibody mediated immunity B cells indirectly attack targets by labelling them for destruction.
What is similar between B and T cells?
- specific to antigens
- clone in response to activation
- form a memory pool (and increased secondary response)
What’s the main difference in B and T cell activation?
T cells only activate when foreign antigen is presented together with a self-antigen on the surface of a body cell
What are the three types of T cells?
- cytotoxic (killer) T cells
- helper T cells
- regulatory T cells
What is the role of cytotoxic T cells?
Destroy host cells that present foreign antigen on their surface in conjunction with MHC self-antigen (ex. virus-infected cells, cancerous cells)
What protein is released by killer T cells and what does that protein do?
perforin, which forms large pores in the target cell, leading to lysis
What is the main role of helper T cells?
secrete cytokines that augment nearly every aspect of immune system (most cytokines produced by them)
What cell type does HIV target?
Helper T cells
What do regulatory T cells do?
suppress both innate and adaptive immune responses in a check-and-balance fashion to minimize harmful effects of the immune response
What is the difference between Class I and Class II major histocompatibility complex glycoproteins?
Class I: found on all nucleated body cells
Class II: found only on macrophages, dendritic cells, and B cells
Which T cells are activated by which?
Class I: cytotoxic T cells
Class II: helper T cells
What is a dendritic cell? What does it do?
phagocyte similar to macrophages, abundant in body tissues. After engulfing foreign material, it migrates to lymph nodes to present antigens along with class II MHC glycoproteins to helper T cells.
What is a tumor cell?
mutation occurs within genes that regulate cell division and growth, leads to unrestricted multiplication of the cell
What is meant by immune surveillance?
recognition and destruction of new, potentially cancerous tumor cells by T cells
What is the difference between benign and malignant tumors?
benign: slow growth, does not infiltrate surrounding tissue
malignant (cancer): fast growth, infiltrates surrounding tissue
What does metastasis mean?
malignant tumor cells don’t adhere well to surrounding tissue; can break away and travel thru bloodstream to other areas of the body
Which cells work together to prevent cancerous cells from multiplying? What do they secrete?
cytotoxic T cells, natural killer cells and phagocytes
Secrete interferon
How does interferon prevent cancer growth?
it breaks down messenger RNA and inhibits protein synthesis
What are defensins?
antimicrobial peptides that disrupt membrane of microbes
What are the two layers of the skin? Which lymphoctye is scattered throughout these layers?
epidermis and dermis
T cells
Functions of melanocytes
produce the pigment melanin, which absorbs UV rays that could cause mutation in skin cells
Functions of keratinocytes
most abundant, specialize in keratin production, secrete cytokines that influence maturation of T cells in the skin
Functions of Langerhans cells
dendritic cells that present antigen to T cells
Functions of Granstein cells
activate regulatory T cells to put an end to immune response
What do sweat glands secrete?
cooling evaporation
What do sebaceous glands secrete?
oil (sebum) to waterproof skin and keep it from cracking
How do sebaceous glands and sweat glands relate to the immune system?
both contain chemicals toxic to bacteria
