Pathophysiology

Question 1

WBC

Answer 1

Leukocytes (monocytes, lymphocytes, granulocytes-neutrophils, eosinophils, basophils)

Neutrophils- phagocyte

Eosinophil- not phagocytic but release heparin, histamine, bradykinin, serotonin and leukotrienes

Monocytes/macrophages/dendritic cells- phagocytic. Named depending on place- histocyte( connective tissue), kupffer cells (liver), alveolar macrophages (lung), microglia (brain). Antigen presenting cells that activate immune responses in B and T cells. Drawn to damage and released from damaged cells by chemotaxis

Lymphocytes- (T cells, B cells, natural killer cells)- monitor body for cancerous cells and eliminate them

• T cells mature in thymus gland. On contact with APC (antigen presenting cells) mature into helper T cells, cytotoxic T cells or memory T cells
• B cells on contact with antigen mature to plasma cells (secrete antibodies) or memory cells
• natural killer cells- spleen, lymph, bone marrow and blood. Immune surveillance and resistance to infection. Inhibited when come in contact with healthy cells. Detect early cancer cells
• antibodies- bind to antigen to inactivate it. IgG, IgA, IgM, IgD, IgE

Question 2

Lymphatic system

Answer 2

Thymus, and bone marrow (mature B/T cells), spleen, tonsils, lymph nodes

• spleen- only place that filters blood, stores broken down RBC for future use
• lymph fluid- picks up used albumin for reuse
• lymph tissues- mucosa associated lymphoid tissue (MALT), gut associated lymphoid tissue (GALT) help fight gut bacteria without an inflammatory response

Question 3

Cytokines

Answer 3

Released by WBC- interleukin, interferons and tumour necrosis factor

Question 4

Innate inflammatory response

Answer 4

1. Inflammation
2. Vascular response-vasodilation and membrane permeability-fluid moves out of blood into tissue causing oedema and inflammation
3. Cellular response- blood becomes viscous which moves leukocytes to side of blood vessels and they accumulate. Leukocyte adhesion separates endothelial cells and lets leukocytes pass through blood vessel into tissue space. Leukocytes are drawn to damage by chemotaxis signals and engulf dead cells, damaged tissue, bacteria and non-functioning neutrophils
4. Phagocytosis- phagocyte engulfs bacteria and releases bactericidal agents that destroy antigen (oxygen and nitrogen radicals-nitric oxide, hydrogen peroxide, hydroxyl ions as well as digestive enzymes lysosomal that destroy bacteria cell membrane). Healthy cells are not phagocytised due to-smooth surface of cells, electronegative charge, opsonisation (immune response coats bacteria with opsonin which enables phagocytes to bind)

Question 5

Inflammatory mediators

Answer 5

Vasoactive- histamine, prostaglandin, leukotrienes, platelet activating factor

Chemo tactic factors- compliment fragments, chemokines- attract leukocytes to damage

Plasma enzymes- proteases- activate compliment system, clotting cascade and vasoactive kinins

Miscellaneous cell products- oxygen metabolites and lysosomal enzymes- damage surrounding tissue

Question 6

Adaptive immune response

Answer 6

1. Antibody mediated (humoral)- B cells activated by contact with antigen, proliferate and differentiate into antibody producing plasma cells and memory cells
   - antibodies produced by B cells inactivate antigen by- covering it with antibodies to attract phagocytes, precipitation- combining with soluble antigen to form insoluble complex that can be captured and destroyed, neutralisation- combining with antigen to neutralise it and stop from attaching to cells, compliment activation and fixation to antigen cell surface leading to cell lysis, agglutination (clumping) of antigens to form large complex, opsonisation- coating antigen with antibodies
2. Cell mediated response- such as when virus is in cells and doesn’t produce antigen response.
   - T cells proliferate and divide into cytotoxic cells, helper cells, suppressor cells and memory cells
   - cytotoxic cells (CD8)- seeks out and destroys abnormal cells by combining with it and either destroying the cell membrane or releasing cytotoxic substances into the cell
   - helper cells (CD4)- stimulate proliferation of other T cells and B cells to promote their multiplication and conversion into plasma cells capable of producing antibodies
   - suppressor cells- release inhibitory cytokines that inhibit action of T and B cells and limit extent of immune response

Question 7

Antibiotics

Answer 7

Bacteriostatic- inhibit growth of bacteria and leave it to immune system to destroy (erythromycin, tetracycline)

Bactericidal agents- kill bacteria without immune help (penicillin, cephalosporins, aminoglycoside)

Mechanisms for anti microbials

1. Impair cell wall synthesis leading to lysis and cell destruction
2. Inhibit protein synthesis causing impaired function
3. Alter cell membrane permeability causing intracellular content to leak
4. Inhibit synthesis of nucleic acids
5. Inhibit cell metabolism and growth