Immunology: Case Studies 1 Flashcards by Maddie Palmer

What is the immune role of the thymus?

A)NK cell development and selection

B) B lymphocyte development and selection

C) T lymphocyte development and selection

D) Monocyte development and selection

E) Neutrophil development and selection

C) T lymphocyte development and selection

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Patient with digeorge syndrome

Numerous severe viral infections and fungal infections

cleft pallette

wide separated low ears

NO THYMIC SHADOW

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Development if T cells in the thymus

Double negative T cells do not express CD4 or 8

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What best describes T lymphocyte selection in the thymus> After TCR rearrangement comes

A) only negative selection of TLR

b) only positive selection of MHC
c) positive selection and negative selection os TLR
d) positive selection on TLR; negative selection on MHC
e) positive and negative selection on MHC

e) positive and negative selection on MHC

TLR is toll like receptor. They are involved in sensing a pathogen. Dont play a role in T cell development

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Positive selction of T cells

Double positive thymocytes

If receptor binds self MHC class I it will be a CD8 T cell

If binds self peptide MHC class II it will become CD4T cell

Negative selection happens to get rid of. cells that react to strongly to self peptides/antigen

If binding affinity high, will not be viable

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Negative selection of T cells to kill off cells with high affinity for self antigen

moderate or low binding affinity and cell lives

high affinigty (tight binding) and cell dies

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Blue part is produce TCR and then positive selction

orange part is nagative selection

Mature self-restricted, slef tolerant, single positive CD4 or CD8 T cells leqave the thymus in blood vessels

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What are the main effector functions of T lymphocytes

a) CD4 cytotoxic ; CD8 secrete cytokines
b) CD4 pagocytic; CD8 secrete cytokines
c) CD4 secrete cytokines; CD8 cytotoxic
d) CD4 secrete cytokines; CD8 pagocytic

c) CD4 secrete cytokines; CD8 cytotoxic

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Helper T cell secreting cytokines after microbial antigen presentation by APC which activates macrophages, inflammation, and activation (priliferation and differentiation) of T and B lymphocytes

cytotoxic T lymphocyte
Infected cell expressing microbial antigen
Ag presentation by MHC class I, then killing of infected cell

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The child with digeorge has no detectable thymus (ie no T cells). What innate defense mechanisms are still present to kill viruses?

a) IFN-α and IFN-ß; natural killer (NK) cells
b) phagocytic cells; B lymphocytes
c) pagocytic cells; CD8 lymphocytes
d) Interleukin-2 (IL-2); eosinophils

a) IFN-α and IFN-ß; natural killer (NK) cells

IFN are antiviral

NK cells recognise and kill infected cells
these cells have downregulated MHC class I

Can not be B. phagocytic cells usually not viral killers

B lymphocytes are part of the adaptive immune response, not innate. They also need helper T cells to class switch and activate B cells

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IFN-α and IFN-ß

action against viruses

classificiation

Antiviral activity
activation of NK cells
inhibits viral replicaiton

Innate

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NK cells

action against viruses:

Classification:

Lysis of infected cells

innate

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CD4 T cell

action against viruses:

classification

Produce cytokines to help B cells and CD8 T cells

Adaptive

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CD8 T cell

action against viruses:

classification

Lysis of infected cell; produce cytokines to help NK cells become cytotoxic

adaptive

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B cell

Action against viruses

Classification

Produce antibody; neutralization, opsonization for ADCC

ADCC = antibody dependent cellular cytotoxicity. The lysis of an infected cell

Adaptive

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DiGeorge

22q11

THYMUS DOES NOT DEVELOP

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Bare lymphocyte syndrome

Child with history of bacterial, viral, and fingal infections

long episodes of D

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Bare lymphocyte syndrome lab tests

CBC and differential: normal total number of neutrophils, monocytes, lymphocytes, eosinophils, and basophils

Antibody titers for immunization antigens were negligible

Nitroblue tetrazolium (NBT) test showed normal respiratory bursts after phagocytosis (ie phagocytes can kill)

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Bare lymphocyte syndrome

Based on the infection history and lack of antibody responses, where do you suspect the defect to be?

Natural killer (NK) cells

Lymphocytes

Neutrophils

Eosinophils

Lymphocytes

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What antibodies do

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Which cell population helps B cells make antibody?

NK cells

CD4 lymphocytes

CD8 lymphocytes

Macrophages

CD4 lymphocytes

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Bare lymphocyte syndrome

Flow cytometry shows severe CD4 lymphopenia. Where do suspect the defect?

Complement proteins expression

MHC class I expression

MHC class II expression

TLR expression

MHC class II expression

Why would lack of MHC II mean no CD4 cells? Posisive selection

None can come out of the thymus to periphery

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No CD4 cells = No B cell help

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BLS is a rare autosomal disorder caused by genes that control expresison of what

MHC class II. MHC class II is not expressed on APCs Tx: IV immunoglobulin, bone marrow transplant

In addition to B cells, what other immune cells express MHC class II a) dendritic cells and macrophages b) NK cells and neutrophils c) basophils and eosinophils d) CD4 and CD8 lymphocytes

a) dendritic cells and macrophages

Which cell surface molecule is responsible for presenting viral antigen derived from virus infecting a cell? CD4 CD8 MHC class I MHC class II TLR

MHC Class I Protein being synthesized endogenously. MHC Class I

In humans, what are the MHC genes known as? H-2 B HLA ABO ABD

HLA

Which type of antigen is processed for presentation by MHC molecules? polysaccharides nucleic acid protein glycolipid carbohydrates

PROTEIN

Development of protection in a primary adaptive immune response to a T dependent antigen takes approximately how much time? 30-120 mins 6-24 hours 1-4 days 1-3 weeks 2-6 months

1-3 weeks

Increase in memory cells after priming means that the secondary response is fater and greater

LAD-1 Leukocyte adhesion deficiency

8 year old F with recurrant necrotic infections to the arms and legs.

LAD-1 Lab tests

CBC diff: normal Complement levels and function: normal Nitroblue tetrazolium (NBT) test: normal Serum Ig (total levels) : normal Antibody titers for vaccine antigens: normal

What cell type is rapidly recruited to the site of a bacterial infection in the skin? eoinophils neutrophils basophils NK cells

Neutrophils

What role do neutrophils play in an immune response against a pathogen? a) antigen presentation to CD4 lymphocytes b) induce B lymphocytes to make antibody c) phagocytose and kill foreign pathogens d) activate NK cells

c) phagocytose and kill foreign pathogens

Neutrophil function and what they express

Neutrophils stored in bone marrow and are released when needed to fight infection They travel to and enter the infected tissue wher they engulf and kill bacteria. They die in the tissue and are engulphed and degraded by macrophages Neutrophils express receptors for many bacterial and fungal constituents Neutrophils bind bacteria, engulf them, and destroy them with the toxic components of the neutrophil granules

Neutrophils were prominent in the patient's blood and were functional, but were not observed at the site of the infection. What molecule is most likely defective? pattern recognition receptor complement MHC class I Integrins

INTEGRINS

The child has been diagnosed with leukocyte adhesion deficiency 1 (LAD-1) due to the defect in CD18 (a component of beta-2 integrin/LFA-1

If you look at the picture, you can see that LFA-1 is important in binding and rolling for neutrophil adhesion and entering into tissue. Thus cell can not get into tissue and can not fight infection

LAD 2

Trafficking defect due to defects in carbohydrates present on the leukocyte cell surface Carbohydrates are the ligands for P selectin and E selectin Cell rolloing to slow down the leukocyte does not occur

What is one immune function of the spleen a) capture lymphatic borne antigen b) capture blood borne antigen c) capture mucosal associated antigen

b) capture blood borne antigen lymphatic borne antigen is captured in the LN

What is the function of the red pulp? Remove aged or abnormal RBCs Activate eosinophils Generate antibodies Activate NK cells

Remove aged or abnormal RBCs | (white pulp is analogous to LNs)

Howell-Jolly bodies in blood smear. Inclusions are formed by the retention of nuclear remnants in red cells which are usually removed by spleen

What is the function of the white pulp? Mast cell activation Secrete complement factors Interactions between B and T lymphocytes Activate NK cells

Interactions between B and T lymphocytes

Ways antibodies eliminate pathogens

neutralization opsonization

Neutralization

Ab binds to pathogen in a way that inhibits pathogen growth, replication, or interaction with human cells; Ab binds to toxin to inhibit activity

Opsonization

coating of pathogen with Ab/ Ab+ complement for efficient phagocytosis

Ways that Abs eliminate pathogens neutralization and opsonization

Most common and rapidly progressing infections after splenectomy are

streptococcus pneumoniae and haemophilus influenzae Encapsulated pathogens that can enter the bloodstream eliminated by innate and adaptive immune respinses in the spleen

Asplenic patients are given what as treatment

antibiotic prophylaxis

Complex immunodeficiency

31 year old F with nasal perforation and ulcerated brown-violet skin lesions Hx TB

Complex immunodeficiency labs

Leukocytes : normal Lymphocytes: normal T cells (CD3+): Normal CD4 T cells: Normal CD8 T cells: Absent (αß) CD4- CD8- γδ T cells: High B cells: normal IgG: Low Other Ig: Normal Note γδ T cells are a specialized calss of T cells that are not selected in the thymus and are not MHC restricted. They are resident to epithelial surfaces.

Complex immunodeficiency Where do you suspect the defect? B lymphocyte development and selection T lymphocyte development and selection Monocyte development and selection Neutrophil development and selection

T lymphocyte development and selection

What mechanism of genetic recombination occurs in developing T lymphocytes that leads to the generation of the TCR somatic hypermutation somatic recombination allele polymorphism affinity maturation

Somatic recombination AKA VDJ recomb. Somatic hypermutation is the mutagenesis of B cells Affinity maturation happens due to somatic hypermutation

Complex immunodeficiency Where do you suspect the defect? MHC class I MHC class II RAG CD3

MHC class I

In complex immunodeficiency you do not have MHC class I and this can not self bind. Can not get CD8 cells bc of this.

Complex immunodeficiency labs FcRn (brambell receptor) CD-1 expression

FcRn (brambell receptor): ABSENT CD-1 expression: ABSENT

FcRn AKA

FcRB (brambell receptor)

What does FcRn (FcRB) do?

It helps increase the half life of IgG molecules Responsible for maternofetal trandfer of IgG and normal IgG and albumin half-life

Defective FcRn

Low IgG

FcRB carries IgG acrosss endothelium into extracellular spaces

Complex immunodeficiency: Why the dysfunction in: MHC class I FcRn/FcRB CD1

They all share the ß2-microglobulin as part of their structure

Where do MHC class I molecules bind peptide? Endosome compartment Golgi apparatus Endoplasmic reticulum Cytosol

Endoplasmic reticulum

MHC Class I pathway

Notice that TAP loads peptides onto MHC Class I. TAP deficiency can also lead to lack of MHC class I expression Mutations in TAP are the most common cause of MHC Class I deficiencies

What cells express MHC class I? Only DC, B cells, macrophages All nucleated cells, but not DCs, B cells, macrophages All nucleated cells

All nucleated cells

Proteins processed by the endogenous vs the exogenous pathway ``` Endogenous- MHC class I expressed on nucleated cells Presents viral and tumor antigens ``` ``` Exogenous- MHC class II expressed on limited number of cells (mainly DCs, macrophages, B cells) Presents viral, bacterial,fungal, and environmental antigens ```

The pt with complex immunodeficiency was diagnosed with B-2 microglobulin

Hypogammaglobulinemia and hypoalbuminemia due to lack of expression of FcRn/FcRB Deficiency in clearing extracellular pathogens ``` No CD8 Tc cells in blood due to no MHC class I expression deficiency in clearing intracellular pathogens ```

Immunology: Case Studies 1 Flashcards

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