Immune System

Question 1

• transport oxygen (to tissues) and CO2 (away from tissues)
• help buffer pH
• most abundant

Answer 1

erythrocytes

Question 2

• pinched-off cytoplasmic fragments of specialized bone marrow cells involved in blood clotting
• adhere to collagen fibers exposed by damage to endothelial cells of blood vessels
• release factors that make its cells more “sticky” and convert the plasmid protein prothrombin to thrombin, which (eventually) helps convert the plasmid factor fibrinogen to fibrin

Answer 2

platelets

Question 3

neutrophils, basophils, eosinophils

Answer 3

granulocytes (aka polymorphonuclear leukocytes)

Question 4

• numerous lysosomes and secretory vesicles
• phagocytic
• attracted to and enter infected tissues
• especially effective against bacteria and fungi
• release neutrophil extracellular traps (NETs)
• one of the two main “professional phagocytes”

Answer 4

neutrophils

Question 5

• synthesize and secrete histamine
• arterioles dilate and capillary permeability increases
• leads to edema, redness, and heat
• secrete heparin, which modulates clotting
• similar to Mast cells found in connective tissue

Answer 5

basophils

Question 6

• low phagocytic activity but critical to defense against multicellular parasites
• secretes toxic proteins

Answer 6

eosinophils

Question 7

monocytes and macrophages

Answer 7

agranulocytes (aka mononuclear leukocytes)

Question 8

• only circulate for a few hours and then migrate into tissues and transform into macrophages

Answer 8

monocytes

Question 9

• large, long-lived cells
• phagocytic via pseudopodia and phagosomes
• some migrate throughout body while others reside in various organs and tissues (i.e. spleen and lymph nodes)
• one of two main “professional phagocytes”
• use nitric oxide and enzymes like lysozyme
• important antigen-presenting cell, esp. during secondary immune responses

Answer 9

macrophages

Question 10

a major antigen-presenting cell type, esp. during primary immune response; ex: Langerhans cells in skin

Answer 10

dendritic cells

Question 11

NK cells, B cells, T cells, CD8+ cells, CD4+ cells

Answer 11

lymphocytes

Question 12

• activated by alpha (secreted by virus-infected leukocytes) and beta (secreted by virus-infected fibroblasts or epithelial cells) interferons
• produce gamma interferon (as do activated T-cells), which helps activate macrophages
• kill by apoptosis (cytotoxic, but not by phagocytosis)
• part of innate immune system
• especially effective against viral-infected cells and cancer cells

Answer 12

natural killer cells

Question 13

• develop in the bone marrow
• epitope-specific Y-shaped receptors (known as B-cell receptors)
• recognize intact, native state epitopes
• secrete antibodies
• after clonal selection, they form short-lived effector cells (aka plasma cells) and long-lived memory B-cells
• antibodies include IgM, IgG, IgA, IgE, and IgD

Answer 13

B cells

Question 14

• develop in the thymus
• epitope-specific I-shaped receptors (known as T-cell receptors)
• recognize small fragments of antigens that are bound to normal cell-surface proteins called major histocompatibility complex (MHC) proteins
• known for antigen-presentation
• after clonal selection, T cells form short-lived effector cells (activated helper T cells and active cytotoxic T cells) and long-lived memory helper T-cells and memory cytotoxic cells

Answer 14

T cells

Question 15

• cytotoxic T-cells
• recognize Class I MHC, which display antigen fragments that were synthesized within the cell due to infection or a cancerous state (Class I MHC molecules are found on almost all nucleated cells)
• releases perforin molecules, which form pores, and proteolytic enzymes (granzymes) taken up by endocytosis; this leads to apoptosis

Answer 15

CD8+ cells (binds MHC 1)

Question 16

• Helper T-cells
• recognize Class II MHC, which display antigen fragments resulting from phagocytosis and/or endocytosis (Class II MHC molecules are found only on antigen-presenting cells like dendritic cells (particularly important with naïve helper T-cells and so in the primary immune response), macrophages (particularly important with memory helper T-cells and so in the secondary immune response), and B cells (which, however, can internalize and present only the antigen to which it specifically binds, unlike dendritic cells and macrophages))

Answer 16

CD4+ cells (binds MHC 2)

Question 17

• first Ig class produced by plasma cells after initial exposure to antigen; then its concentration in the blood declines
• promotes neutralization (coats antigen so they can’t bind to cells in the body) and cross-linking of antigens (i.e. clumping of flu virus); very effective in complement system activation
• pentamer

Answer 17

IgM

Question 18

• most abundant Ig class in blood
• present in tissue fluids
• crosses placenta, thus conferring passive immunity on fetus
• monomer

Answer 18

IgG

Question 19

• present in secretions such as tears, saliva, mucus, and breast milk
• presence in breast milk confers passive immunity on nursing infant
• dimer

Answer 19

IgA

Question 20

triggers release from mast cells and basophils of histamine and other chemicals that cause allergic reactions

Answer 20

IgE

Question 21

• acts as antigen receptor in the antigen-stimulated proliferation and differentiation of B cells (clonal selection)
• B cell receptor (monomer with trans-membrane region)

Answer 21

IgD