immunity - host defence mechanisms

Question 1

features of innate immunity

Answer 1

• skin
• gastric acid
• mucociliary escalator
• phagocytic cells (ingest foreign bodies)

Question 2

types of phagocytic cells (3 polymorphs and 1 other)

Answer 2

polymorphs: neutrophile, eosinophils, basophils

+ monocytes in blood which mature into tissue macrophages

Question 3

non-phagocytic lymphocytes (2)

Answer 3

• T cells (mature in the thymus)

- B cells

Question 4

process of phagocytosis

Answer 4

• ingestion
• organism held phagosome
• fusion with lysosome
• phagolysosome
• intracellular killing

Question 5

organisms resistant to phagocytosis and intracellular killing

Answer 5

• capsulate organisms (eg strep pneumonia) resistant to phagocytosis
• others (e.g. mycobacterium tuberculosis) resistant to intracellular killing

Question 6

features of mononuclear phagocytic system

Answer 6

• spleen clears blood
• liver clears enterohepatic circulation
• regional lymph nodes drain peripheral sites

Question 7

describe oponisation

Answer 7

• organism coated with antibody or complement
• phagocytic cell has receptors for both
• efficiency of phagocytosis is greatly improved
• particularly important for capsulate bacteria

Question 8

describe acquired immunity

Answer 8

• is a specific response to the antigen concerned
• immunological memory created
• humoral (antibody) and cellular (T cells)
• each organism is a complex mixture of antigens and each antigen is (usually) a mixture of epitopes

Question 9

different immunoglobulins used in different responses

Answer 9

• immunoglobulins are the proteins with antibody activity:
• primary response; IgM
• secondary response; IgG
• mucosal immunity; IgA
• allergy and helminth infection; IgE

Question 10

function of B-lymphocytes in immunity

Answer 10

• B-lymphocytes differentiate into plasma cells when they recognise a specific epitope
• they require help from T-cells (CD4 T-cells)

Question 11

function of monoclonal antibodies

Answer 11

form from one clone of plasma cells that has specificity for a single epitope

Question 12

polyclonal antibody function

Answer 12

has multiple specificity/acts on more than one epitope

Question 13

what triggers a compliment cascade?

Answer 13

a combination of antibody (IgG or IgM only) and its specific antigen

Question 14

qualities of antibodies in infection (5)

Answer 14

• neutralises bacterial toxins
• neutralises viruses in viraemic stage
• prevents adherence of microorganisms
• oponises capsulate organisms
• can be a useful means of diagnosis (serology)