Microbiology 🦠 Flashcards

Question

What is the Treatment of staph aureus?

Answer 1

Penicillinase-resistant β-lactams.

Answer 2

- S. epidermidis | - S. saprophyticus

Answer 3

Normal flora of the skin, nonpathogenic.

Answer 4

It may cause infections in immunocompromised individuals & infections on prosthetic implants such as heart valves and hip joints.

Answer 5

Causes UTI in young females.

Answer 6

S. Aureus is positive to “AEH CDM” protein A, exotoxin production, hemolysis production, coagulase, DNase, and mannitol fermentation. While S. Epidermedis and S. saprophyticus are negative to all of them

Answer 7

S. saprophyticus tests positive to resistance to novobiocin.

Answer 8

Substance recognized by immune system which may be: ✓ Simple or complex ✓ Carbohydrate, lipid, protein, nucleic acid, phospholipids

Answer 9

- B cell recognize any biological Ag | - T cell recognize peptide Ag presented on MHC

Answer 10

Smallest part on Ag which bind with BCR & T cell receptors

Answer 11

it is called multivalent Ag

Answer 12

Depending on the nature of immune responses they trigger, antigens/epitopes are divided into 3 fuctional types: - Immunogens - Haptens - Tolerogens "all the body" "cells that attack them are killed"

Answer 13

Large Ag with epitopes capable of binding with immune receptor & inducing immune response. (Notice that not all antigens are immunogens)

Answer 14

- A small Ag with epitopes capable of binding with immune receptor & without inducing immune response - BUT can produce immune response only when conjugated with large carrier molecule (as a protein) → immune response against epitopes of hapten & carrier.

Answer 15

Self Ag (MHC) normally "but may cause in pathological cases" not stimulate immune system

Answer 16

size:- Proteins > 10 KDs are more immunogenic Complexity:- Complex proteins with numerous, diverse epitopes are more to induce an immune response than are simple peptides that contain only one or few epitopes. Conformation and accessibility:- Epitopes must be “seen by” and be accessibile to the immune system. "Particles in the eye are not accessible" Chemical properties: ✓ A protein is good immunogens. ✓ Many charbohydrates, steroids, and lipids are poor immunogens. ✓ Amino acids and haptens are, by themselves, not immunogenic

Answer 17

- T-cell independent Ag (TI): Activate B cells without help from T cell; e.g. polysaccharides (Pneumococcal polysaccharide, LPS) - T-cell dependent Ag: Requires T cell help for B cell activation, e.g. proteins (microbial proteins & non-self or altered-self proteins).

Answer 18

- In lymph node → Ag stimulation of B cells with help of T helper cytokines → B cell proliferate → differentiate into plasma cell which secrete antibodies → enter circulation → site of infection - Also mature B cell in Bone Marrow express membrane bound antibodies (BCR) - So antibodies are produced in lymphoid tissue & bone marrow

Answer 19

Secreted: "99%" ✓ In plasma & mucosa & interstitial fluids of tissues Membrane-bound Ig: ✓ Expressed on B cell surface (IgM & IgD) as BCR for Ag ✓ If bind with Ag, initiate B cell response

Answer 20

- Y shaped molecules of 4 polypeptide chains - 2 identical heavy chain (1 variable domain (VH) and 3 or 4 constant domains (CH) - 2 identical light chain (1 variable domain (VL) and 1 constant domain (CL) - Each variable domain (VL or VH) contains 3 hypervariable regions called complementary determining repeats (CDR) - Disulfide bonds connect heavy chain with light chain & heavy chain with heavy chain.

Answer 21

Hinge region: • Flexible region lies between Fab & Fc to give mobility to both Fab to accommodate different Ag ``` Fc (fragment crystalline) • Tend to crystallize in solution • 1 in number • Contain remaining of both heavy chains C domain. • Effector & biological function. ``` Fab = Fragment antigen binding * Contain whole light+VH+ CH1 * 2 in number * Ag recognition and binding

Answer 22

- Immunoglobulins →divided into five different classes → according to the difference in structure in constant domains of heavy chain ```  Gamma heavy chains → IgG  Alpha heavy chains → IgA  Mu heavy chains → IgM  Epsilon heavy chains → IgE  Delta heavy chains → IgD ``` - Different classes and subclasses of antibodies perform different effector functions

Answer 23

- There are two types of light chains, called κ (kappa) and λ (lambda). - An antibody has either two κ or two λ light chains.

Answer 24

- Is the switch from one Ig isotype to another. - After activation of B lymphocytes, a specific clone of B cells proliferate and differentiate into progeny that secrete antibodies; some of the progeny secrete IgM, and other progeny produce antibodies of different isotypes

Answer 25

IgA 1 and IgA 2

Answer 26

Alpha-1 and alpha-2

Answer 27

Monomer, dimer and trimer

Answer 28

Mucosal immunity

Answer 29

B-cell receptor

Answer 30

- Parasite | - allergy

Answer 31

IgG1 – IgG4

Answer 32

Gama 1,2,3,4

Answer 33

- Opsonization - Complement - ADCC

Answer 34

B-cell receptor and compliment

Answer 35

- Identical monospecific antibodies that are produced by one type of immune cell that are all clones of a single parent cell.

Answer 36

- In contrast, antibodies obtained from the blood of an immunized host are called polyclonal antibodies.

Answer 37

- A mouse is immunized with the antigen - B cells are isolated from the spleen of the mouse. - B cells (Anibody-producing cell) are then fused with myeloma cells (malignant cell) in vitro by using a fusion agent as poly-ethylene glycol, a virus. - The cell fusion forms an antibody-producing cell “hybridoma”. - Hybrids (fused cells) are selected for growth in special culture media - The B cells that fuse with another B cell or do not fuse at all die because they do not have the capacity to divide indefinitely. - Only hybridomas between B cells and myeloma cells survive. - Hybridomas, secrete a large amount "and indefinitely" of mAbs.

Answer 38

- Identification of phenotypic markers: They have been used to define clusters of differentiation (CD markers) "4-8" on lymphocytes. - Immunodiagnosis: The diagnosis of many infectious and systemic diseases relies on the detection of specific antigens or antibodies in the circulation or tissues by use of mAbs. - Tumor diagnosis: Tumor-specific monoclonal antibodies are used for detection of tumors by imaging techniques. - Therapy: "Drug associated with monoclonal antibodies for specific target" A number of mAbs are used therapeutically today: Anti-CD3 for immunosuppression and prevention of graft rejection

Answer 39

1) Humoral (Antibody - Mediated) Immunity. | 2) Cell-Mediated Immunity.

Answer 40

mediated by secreted antibodies

Answer 41

Its physiologic function is defense against extracellular microbes and microbial toxins

Answer 42

1) Neutralization of microbes and microbial toxins 2) Opsonization and phagocytosis 3) Antibody-dependent cell-mediated cytotoxicity (ADCC) 4) Activation of the complement by IgG and IgM "pathogen---> no reaction. Pathogen with AB ----> Reaction" 5) Functions of antibodies at special sites

Answer 43

- Antibodies blocks and prevent binding of microbe to cells i.e. prevent infection of cells. "So that we don't even need cell mediated immunity" - Antibodies inhibit the spread of microbes from an infected cell to an adjacent cell. - Antibodies block binding of toxin to cellular receptors, and thus inhibit pathologic effects of the toxin.

Answer 44

Antibodies of IgG isotype opsonize (coat) microbes

Answer 45

- IgG bind to infected cells by the Fab regions, and bind by Fc to Fc receptors on NK cells. - The NK cells are activated and kill the cells. - IgE "+IgG" bind to helminthic parasites by the Fab regions, and bind by Fc-to-Fc receptors on eosinophils. - The eosinophils are activated to release their granule contents, which kill the parasites.

Answer 46

Mucosal immunity Neonatal immunity

Answer 47

- IgA is the major class that is produced by the mucosa-associated lymphoid tissues (MALT) in the GIT and RT and transported to the lumens of organs. - In mucosal secretions, IgA binds to microbes and toxins present in the lumen and neutralize them by blocking their entry.

Answer 48

- neonates are protected from infection by maternal antibodies (IgG) "produced by mother" transported across the placenta into the fetal circulation and by antibodies in ingestd milk transported across the gut epithelium of newborns. "But they are passive antibodies which last for six months" "Newborns have good immunity to most infections that have have infected the mother"

Answer 49

- When we are exposed to an antigen for the first time: a) There is a lag of several days (10 days) before a specific antibody becomes detectable. b) This antibody is IgM. c) After a short time , the antibody level declines.

Answer 50

If at a later date we are re-exposed to the same antigen, there is a) more rapid appearance of antibody, greater amount. b) IgG class. c) remains detectable for months or years.

Answer 51

the properties of the specific response to this antigen are those of the primary response

Answer 52

Onset: rapid - slow Magnitude: High - low Lifetime: long - short Isotype: IgG (Or IgA, or IgE) - IgM

Answer 53

- because the immune system possesses specific immunologic memory for antigens. - During the primary response, some B lymphocytes, become memory cells which are long lived.

Answer 54

Thus we can see that the secondary response requires the phenomen known as class switching (IgM to IgG).

Answer 55

Eradicates infections by intracellular microbes.

Answer 56

- Consist of the activation of naïve T cells to proliferate and differentiate into effector cells (CD4+ T helper cells and CD8+ cytolytic cells; CTLs) and the elimination of the intracellular microbes

Answer 57

CD4+ T cells: Differentiate into 2 effector cells according to cytokine production by antigen presentig cell:  IL-12 leads to Th1  IL-4 leads to Th2  Th1 secrets IFN-g activates phagocytes to kill microbes.  Th2 secrets IL-4 and IL-5 which stimulate eosinophil and mast cell degranulation in allergy and helminthic infection CD8+ T cells: kill any cell containing microbes or microbial proteins in the cytoplasm (intracellular) by direct cell cytotoxicity,; eliminating the reservoir of infection .

Answer 58

Activated by two signals - The 1st signal: peptide + MHC on the surface of APCs recognized by TCRCD3. - The 2nd co-stimulatory signal: is the interaction of B7 molecule on APCs with CD28 on T cells.

Answer 59

exposure of T cells to antigen lead to anergy (unresponsiveness)

Answer 60

1) CTLs recognize class I MHC + peptides on the surface of infected “target” cell”. 2) Formation of tight adhesions “conjugates” with these cells. 3) CTLs are activated by IL-2 & IFN-γ to release their granule contents toward the target cell i.e. granule exocytosis. 4) The granules contents include: - Perforin, which form pores in the target cell membrane - Granzymes enter the target cells through these pores and induce apoptosis through the activation of caspases. 5) Detachment of CTL from target cells to kill other target cell. 6) Death of target cell.

Answer 61

- Group of genes on short arm of chromosome 6 which produce MHC molecules present on cell surfaces and responsible for display of protein Ag to T cell Also called human leucocytic Ag = HLA

Answer 62

1) Class I MHC genes → HLA-A "human leucocytes antigen" & HLA-B & HLA-C → role in Ag presentation to Tc 2) Class II MHC genes → HLA-D region (HLA-DR & HLA-DP & HLADQ) → role in Ag presentation to Th 3) Class III MHC genes → lies between class I & II & not produce MHC but produce some complement components & TNF-α.

Answer 63

- Are membrane proteins expressed on cells. - Each class I & II molecule consist of extracellular part, a transmembrane and a cytoplasmic part to anchore the molecule to the cell.

Answer 64

- polypeptide chains, α chain formed of 3 domains (α1, α2, α3), attached to a polypeptide chain called β2 microglobulin encoded by a gene outside MHC. - α1 and α2 domains form the cleft or groove which bind peptide. - Present antigen to CD8+ cells. - Class I molecules are expressed on all nucleated cells.

Answer 65

- 2 polypeptide chains α chain (α1 & α2) and β chain (β1 & β2). - α1 and β1 domains form the peptide binding cleft. - Present antigen to CD4+ cells. - Class II is expressed on APCs only.