adaptive immune system (adaptive immunity, B and T cell development, and adaptive immune response to pathogens)

which lymphocyte is cell-mediated immunity?

T cell

which lymphocyte is involved with humoral immunity?

B cells

what are the properties of a good immunogen?

1. large molecular size (>1000 Daltons)

2. complex proteins or glycoprotein

3. stability

4. foreigness

what is the type of response of the immune system to a recognized hapten?

humoral immune response (antibody is generated)

what are two mechanisms for lysing RBCs coated with antibody?

1. complement activation via the classical pathway

2. host cells expressing receptors for the Fc part of the antibody

what are some clinical examples of cross-reacting antibodies?

1. brucella abortus

2. autoimmune conditions

3. RBC blood types

explain cross-reacting antibodies of brucella abortus

certain bacteria strains share epitopes that provoke cattle to make antibodies to cross-react with B. abortus epitopes. Thus cows may wrongly be thought to have B. abortus

what are good immunogens in bacteria?

gram-negative bacterial pilli, flagella, and cell wall proteins

what are examples of non-microbial antigens?

1. RBC glycoprotein

2. MHC molecules

3. CD molecules

what does the MHC refer to?

nucleic acids that code for the MHC molecules (proteins)

which MHC molecule is presented to T-helper cells?

MH-2

what cells present MH-2 to T-helper cells?

1. dendritic cells

2. macrophages

3. B-cells

what does the presentation of MH-2 to T-helper cells provide to the T-helper cells?

provides cytokines to help B-cells and CTLs become activated

which MHC molecule is presented to CTLs?

MHC-1

which cells present MHC-1 to CTLs?

host infected cell or tumor cells

what is the source of peptides for the antigen targeted by CTLs?

proteins made inside the infected or tumor cell (intracellular)

what characterizes the end results of an adaptive CELL-MEDIATED immune response?

formation of effector cells (CTLs and T-helper cells)

the ______ molecule expressed by _______ cells must bind the _________ molecule on the ___________

1. CD4

2. T-helper

3. MHC-2

4. pro/semi-pro

2 multiple choice options

the ________ molecule expressed by _______ must bind the ____ on the ________ cell

1. CD8

2. CTLs

3. MHC-1

4. host infected/tumor

1 multiple choice option

what happens when B-cells function as APCs?

1. bind antigen with their BCR

2. internalize and process the antigen

3. present antigen via MHC-2 molecules to T-helper cells

how do B-cells get cytokine help from T-helper cells?

1. antigen binds in MHC-2

2. MHC-2 on surface of B-cell presented to TCR

3. CD4 recognizes MHC-2 and stimulates pathway

describe the activation of CTL effector cell

1. TCR binds the antigen and MHC-2 complex to the CD4 receptor on the host infected/tumor cell

2. the Th-1 cell has become activated, can clonally expand and help send cytokines

3. CTL receives cytokine help from Th-1 cell and is not activated once it sees antigen of interest

when do we want a cell mediated immunity?

when dealing with intracellular pathogens

T-helper cells help with both...

humoral immunity and cell-mediated immunity

what are the adaptive immune cells/produces that will be generated when dealing with an intracellular microbe?

1. activated CTLs

2. Th-1 cytokines activated macrophages

3. DTH

what ensures that the humoral immune response dominated in extracellular infections?

pro/semi-pro APCs present to Th-cells using MHC-2

what ensures that CMI with the generation of antigen-specific CTLs dominates with intracellular infections?

host cells present to CTLs using MHC-1

what cells respond to the presented antigen when dealing with extracellular microbial antigens?

T-helper cells

how can microbial antigens outside of cells get presented to CTLs and generate a cell-mediated immune response?

dendritic cells and macrophages can engulf antigens outside of cells and shuttle some of the antigen fragments into the pathway for presentation to CTLs via MHC-1 molecules

why are dendritic cells and macrophages able to present MHC-1 cells to CTLs?

they have a nucleus

what components are involved with adaptive immunity when dealing with intracellular stages of pathogens?

1. CTLs

2. DTH response

what cytokines do Th-1 make?

1. interferon gamma (IFN-g)

2. interleukin 2 (IL-2)

what are the two main types of T-helper cells?

1. Th-1

2. Th-2

what cytokines do Th-2 make?

1. interleukin 4 (IL-4)

2. interleukin 5 (IL-5)

Th-1 cytokines promote which type of adaptive immune response?

cell-mediated immunity

Th-2 cytokines promote which type of adaptive immune response?

humoral (antibody) immunity

what do we not have vaccines against in vet med?

1. heartworms

2. tapeworms

what is most effective against protozoa with intracellular stages?

Th-1 cytokine response and good cell-mediated immunity (CTLs and activated macrophages)

what happens when parasite-specific antigens bind to the IgE Fab region?

mast cells degranulate

what will macrophages cause in a helminth infection?

macrophages will help wall off and destroy the parasire into components or fragments (granulomas)

why are fungal infections a challenge for the immune system?

large colony size hard for immune system to control

what does the innate immune response to fungal infections often result in?

acute inflammation

what is the most helpful response to fungal infections?

antigen-specific activation of T-helper 1 cells and the production of IFN-y with enhancement of macrophage function

what does the adaptive immune response to fungal infections often result in?

granulomatous (chronic inflammation)

why are fungi so good at evading immune system?

outer cell wall made of polysaccharide that will not be recognized by immune system and allows intracellular portion with pathogen to avoid immune recognition

B-cells

lymphoid stem cells that remain in bone marrow

T-cells

lymphoid cells that migrate to the thymus

what does it mean if a lymphocyte is "mature"?

immunocompetent, can respond to antigen

what does it mean if a lymphocyte is "naive"?

have not yet encountered their antigen

what should T and B cells leaving the primary lymphoid tissues NOT HAVE?

antigen receptors for "self" antigens

what does negative selection mean in reference to lymphocytes?

death by apoptosis because cell receptor for lymphocyte recognized "self" molecule

what occurs at primary lymphoid tissues?

development and maturation

what occurs at secondary lymphoid tissues?

B and T cell encounter the antigen

what are the sites where lymphocytes respond to antigens?

1. tonsils

2. spleen

3. lymph nodes

4. peyer's patches

what are the sites of lymphocyte development?

1. thymus

2. bursa

3. peyer's patches

4. bone marrow

when do B and T lymphocytes aquire their unique antigen-specific receptor?

when tehy are in their primary lymphoid organs

Peyer's patches can be a site of _______ maturation and development, not _______

1. B-cell

2. T-cell

1 multiple choice option

somatic gene rearrangement

process by which T and B cells create diversity of distinct cell surface molecules

what does somatic gene rearrangement require?

enzymes that can cut and rejoin pieces of DNA

1 multiple choice option

where are the only somatic cells where gene rearrangement occurs?

B and T lymphocytes

where does negative selection of B-cells occur?

bone marrow (and some peyer's patches)

where does negative selection of T-cells occur?

thymus

what is the result of SCID?

foals born lacking functional B and T lymphocytes meaning they can never respond to antigens

what cells are considered lymphocytes?

1. T-cells

2. B-cells

3. NK cells

what type of cells provide structural support for cells of the lymphoid system?

reticular cells (fibroblasts)

the thymus is a _____ lymphoid organ

primary

1 multiple choice option

when does the thymus obtain its maximum size?

during the first few months after birth

when does the thymus become smaller in size?

during puberty

what will the thymus be replaced by in adult animals?

adipose tissue

how do we know that we have residual thymic tissue persisting in adults?

we have continued production of mature but naive T-lymphocytes in the body

if you did a necropsy and saw a thymus, what would the age of that animal be?

young

what would happen if the thymus never developed?

would have no functional CTLs or T-lymphocytes

what is the thymus the site of?

1. T-cell development

2. selection of mature T-cells with TCRs for foreign antigen

where are peyer's patches located?

small intestine mucosa/submucosa

the spleen is considered a ____lymphoid tissue

secondary

what is the immune function of the spleen?

filters blood-borne pathogens, dead RBC, and ANTIGENSin

what is the largest lymphoid organ?

spleen

what is the only lymphoid organ that primarily filters blood?

spleen

what is the primary organ to filter lymph?

lymph nodes

what does the red-pulp of the spleen do?

RBC filtering and storage (NON-IMMUNE FUNCTIONS)

what does the white-pulp of the spleen do?

rich in b and t cells and where adaptive immune responses occur

GALT includes which structure?

peyer's patches

BALT

bronchial associated lymphoid tissue

tonsils

site of induction of adaptive immune responses to antigen entering via the respiratory or alimentary tracts

what happens once lymph is filtered?

fluids returned to blood (veins to heart to systemic circulation)

lymph nodes are ____ lymphoid tissues

secondary

primary follicles of the lymph node dominate when...

there is an absence of antigenic stimulation

secondary follicles dominate when...

there is antigenic stimulation either from infection of vaccination

lymph nodes are the major anatomical site where...

antigenic stimulation of the adaptive immune system occurs

what are the potential reasons why a lymph node may be enlarged after palpation?

1. inflammation

2. infection

3. cancer

how do we distinguish Th-1 cells from Th-2 cells?

by the cytokines they produce

what cytokines do Th-1 cells make after stimulation?

1. interferon gamma (IFN-g)

2. interleukin 2 (IL-2)

what is IGN-g critical for?

activating non-specific macrophages to kill pathogens we are interested in

what cells are activated by Th-1 released cytokines?

1. activated macrophages

2. cytotoxic T cell

what cytokines do Th-2 cells release?

1. interleukin 4 (IL-4)

2. interleukin 5 (IL-5)

what type of adaptive immune response is promoted from Th-1 cytokines?

cell-mediated immunity

what type of adaptive immune response is promoted from Th-2?

humoral (antibody) immunity

what are the two major "effector" categories in adaptive CMI?

1. CTLs

2. DTH response

explain the delayed-type hypersensitivity response (DTH)

interferon-gamma cytokine released from Th-1 cells activated macrophage to kill certain intracellular microbes

what does it mean if we have a strong DTH response?

macrophages have IFN-g so they will be good at killing and pathogen will be eliminated