Microbiology Exam 2

Which types of granulocytes phagocytize pathogens?

Neutrophils and Eosinophils

What type of cell in the bloodstream is the precursor to a macrophage?

monocyte

Increased eosinophils indicates the presence of…

allergies or parasitic worm infection

Increase in leukocytes (mostly neutrophils) indicates presence of…

bacterial diseases

Increase of lymphocytes indicates the presence of…

viral infection

Six stages of phagocytosis

chemotaxis, adherence, ingestion, fusion with lysosome, killing, elimination

How do eosinophils kills parasites?

attaching to surface then secreting toxins that kill or weaken the cell

Toll-like Receptors (TLRs)

integral membrane proteins produced by phagocytic cells

initiate defensive responses

What are TLRs function?

binds pathogen-associated molecular patterns (PAMPS) (PG, LPS, flagellin, viral RNA)

Interferons

protein molecule released by host cells to nonspecifically inhibit the spread of viral infections; cause symptoms of viral infections

Type I interferon

non-immune (alpha and beta)

Type II interferon

immune (gamma)

Complement

set of serum proteins designated numerically according to their order of discovery; activated by cleavage forming peptides

Complement pathways

all function the same way

1) alternate pathway

2) lectin pathway

3) classical pathway

alternate pathway (first)

activated by surface components of microbes directly

lectin pathway (second)

activated by microbial polysaccharides

classical pathway (third)

activated by antibody molecules coating the microbes

Membrane Attack Complex (MAC)

ring of C9 to create pore in pathogen; complex C5b678(9)

C5 Convertase is made up of…

C4a, C2b, C3b

C5a (inflammation)

chemotaxis agent for neutrophils and macrophages

C3a, C5a (inflammation)

anaphylatoxins; histamine release from mast cells

C3b (inflammation)

split product of this binds to cell membranes as opsonin which paints an x on cell as a bad guy

Two types of inflammation

acute (disease and virus) and chronic (long lasting)

local and systemic (throughout the body)

Acute Inflammation

short lived and usually beneficial, vascular and cellular, tissue repair

Vascular Events in Inflammation

dilation and increased permeability of blood vessels, histamine and anaphylotoxins

Cellular Events in Inflammation

migration of phagocytes to site of injury mediated by chemotactic factors, C5a, Interleukin, cytokine, C3b

What stimmulates inflammation?

C3a and C5a fragments of complement cascade cause mast cells to release inflammatory mediators

What triggers a fever?

pyrogens trigger the hypothalamus to increase body temp

antibody-anitgen complexes signal for production of interleukin-I (IL-1) by macrophages

First Line of Defense

skin and mucous membrane prevent the entrance of pathogens; chemicals like sweat enhance protection

Second line of Defense

Phagocytes, Extracellular killing, Complement, Interferons, Antimicrobial Peptides, Inflammation, Fever

B cell

leave bone marrow mature, recognizes antigens, production of antibodies, live in lymph nodes

T Cell

leave bone marrow immature, enter thymus for final development, recognizes pieces of antigen (only if presented by macrophage, dendritic cell, B cell), live in lymph nodes

Dendritic Cells

movement of antigens to nearest lymph node from site of infection;

antigen processing and presentation to T cells

Development of B cell repertoire

genetic rearrangements followed by antigen sampling in bone marrow

Development of T cell repertoire

have to recognize MHC molecule;

genetic rearrangements followed by “education” in the thymus

How does the adaptive immune system communicate?

between cells using receptors and cytokines

What are pathogens role in the lymphatic system?

transport to lymph nodes; activate immune response

what is the path of lymphatic circulation?

leave blood, enter lymph nodes, lymph, return to blood

Do B cells require MHC to recognize antigen?

no

How many binding sites do B cells have?

4

How many binding sites to T cells have?

2 (cannot be secreted & do not make antibodies)

What is an epitope? (antigenic determinants)

minimal 3D region of a non-self molecule that is recognized by an immunoglobulin

Antigens

molecules the immune system recognize as non self and worthy of attack

What are the four functions of antibodies?

Neutralization, Agglutination, Opsonization, Compliment Activation

Neutralization

antibody binds to antigen

Agglutination

formation of cluster

Opsonization

painting of bad guy; recognition

Complement Activation

pathway of the complement

5 Classes of Antibodies

IgM, IgG, IgA, IgE, IgD

IgM

first antibody produced (primary response)

10 binding sites, 5 molecules

IgG

most common and longest lasting (memory response)

IgA

dimeric form associated with mucosal secretions (gut)

4 binding sites, 2 molecules

IgE

involved in response to parasitic infections and allergies

IgD

not secreted

Do T cells need MHC on antigen?

yes

TCR recognizes…

processed antigens (those that have been presented by dendrites, macrophages, B cells); MHC I and II

TCRs only bind to…

epitopes associated with an MHC protein

Can TCR be secreted?

no

Can BCR be secreted?

yes

TCR acts primarily against…

cells that harbor intracellular pathogens

Naive T cells

don’t know the antigen that they are presented to, meaning they have no been activated

Two types of naive cells

CD8+ (MHC class I) and CD4+ (MHC class 2)

CD8+

can become cytotoxic T cells; directly kills other cells

CD4+

can become helper T cells; helps regulate the activities of B cells and cytotoxic T cells

Types of CD4+ cells

Th1, Th2, Tfl (activate adaptive immune response)

To be allowed in periphery, each T cell must….

1) recognize MHC

2) TCR cannot recognize self antigens

Cytokines

cells of immune system communicate by releasing soluble regulatory proteins that act on other cells

Cytokines are secreted by…

leukocytes

Types of Cytokines

interleukins, interferons, growth factors, tumor necrosis factor (TNF), chemokines

interleukins

signal among leukocytes and other tissues

interferons

antiviral proteins that may act as cytokines

Growth Factors

proteins that stimulate the stem cells to divide

Tumor necrosis factor

secreted by Macrophages and T cell to kill tumor cells

Chemokines

chemotactic cytokines that signal leukocytes to move

Exogenous Antigens

enter the body from the outside; inhaling & ingestion

Endogenous Antigens

generated within previously normal cells as a result of normal cell metabolism, or because of viral or intracellular bacterial infection

Non-peptide antigens

also known as T-independent antigens; cannot be loaded on MHC

Exogenous antigens are presented on…

MHC II (phagocytized)

Endogenous antigens are presented on…

MHC I (viral)

MHC I Proteins

expressed on all nucleated cells (not erythrocytes)

HL-A, HL-B, HL-C

MHC II Proteins

expressed on antigen presenting cells such as Macrophages and Dendritic cells

HLA-DR, HLA-DQ, HLA-DP

T cells are located where in the lymph node?

inner

B cells are located where in the lymph node?

outer

How do CD4 T cells become activate?

once associated with APC and antigen with MHC II then activated by TCR

TH1

activates macrophages

TH17

enhance neutrophil response

TH2

activate cellular and antibody response to parasites

TFH

activate B cells maturation of antibody response

Treg

suppress other effector T cells

Naive B cells can go 2 different options

1) straight to the plasma cell (IgM, low affinity)

2) germinal center, 2/3 die off, then death/memory B cell/plasma cell (high affinity)

There is no MHC involvement when..

non-peptide antigens/T-independent antigens

mostly IgM is produced

CTLs use two mechanisms

1) Perforin-Granzyme Pathway

2) CD95 cytotoxic pathway

Are Cytotoxic Lymphocytes tame or wild?

wild- once they start killing, they kill everything

Which becomes activated more efficiently? B or T cells

T cells since they already have an activated phenotype and will proliferate and resume function upon presentation of antigen

Active Immunization (vaccine)

administering antigens so patient can mount an immune response

Passive Immunization (antidote)

individual acquires immunity through transfer of antibodies formed by an immune individual

Who discovered vaccination?

Edward Jenner

Who created the first vaccine?

Louis Pasteur

Attenuated Vaccines

grown in culture so they lose some virulence factors

long term immunity, can cause mild infections but is a strong response

Inactivated vaccines

inject dead organsim

weaker immune response; antigenically weak