Intro to Immuno

Question 1

Primary lymphoid tissue

Answer 1

Bone marrow and thymus

Question 2

Secondary lymphoid tissues

Answer 2

Sites where T and B lymphocytes first contact antigens

Lymph nodes, spleen, and mucosal associated lymphoid tissues (MALT)

Question 3

Polymorphonuclear leukocytes

Answer 3

aka granulocytes:

Neutrophils
Basophils
Eosinophils

Develop from the myeloid lineage in the bone marrow

Question 4

BCR vs. TCR

Answer 4

Question 5

Primary role of innate immune response

Answer 5

Resist initial infection
Induce local inflammation
Faciliatate adaptive response
Promote wound healing

Question 6

Adaptive immune response against extracellular pathogens

Answer 6

Humoral immunity

(Ab’s cannot penetrate intact cells, so ineffective for intracellular paths)

Question 7

Cell-mediated immunity

Answer 7

Primarily mediated by T cells

TCR’s bind antigen-MHC complex

Important defense against both extracellular and intracellular pathogens

Question 8

CD8+ cells

Answer 8

Kill pathogen-infected cells

Only recognize antigen peptides presented on MHC class I proteins (intracellular pathogens)

Question 9

Cells involved in innate immune response

Answer 9

NK cells
Neutrophils
Macrophages
Dendritic cells

Question 10

NK cells

Answer 10

Enter tissues

Sense imbalance between target cell surface MIC (higher) and MHC class I (lower) or the presence of IgG bound to cell surface to recognize intracellular pathogen-infected cells and tumor cells

Targets are killed using perforin and granzymes to induce apoptosis

Question 11

Neutrophils

Answer 11

Circulating WBCs that migrate into sites of tissue infection

Phagocytose and kill ectracellular microbial pathogens and stimulate wound healing after infection is eradicated

Question 12

Macrophages

Answer 12

Tissue resident cells

Phagocytose unicellular bacteria and fungi

Have many different PRRs that bind PAMPs/DAMPs - once activated produce pro-inflammatory cytokines that stimulates local innate and adaptive immune response

Question 13

Waldeyer’s ring

Answer 13

Question 14

What secondary lymphoid tissues helps detect systemic infections

Answer 14

The spleen

Question 15

What MALTs protect the respiratory and GI tract entrance?

Answer 15

The adenoids and tonsils

Question 16

Microfold cells (M cells)

Answer 16

Specialized epithelial cells that deliver antigen across epithelial cell barrier to the underlying MALT

Question 17

First step in activating the adaptive immune response

Answer 17

Activation of pathogenantigen responsive naïve T cells by dendritic cells in 2° lymphoid tissues

Takes roughly 3-4 days

Question 18

What cells initiate the adaptive immune response?

Answer 18

Dendritic cells

Question 19

What stimulates immature DCs to mature?

Answer 19

PAMPs binding to DC PRRs stimulate DCs to mature and migrate to the local secondary lymphoid tissue

DCs can engulf antigen or M cells can also pass antigen across mucosal epithelium to DCs in the underlying MALT

Question 20

CD4+ cells

Answer 20

Helper or regulatory T cells

Recognize antigen peptides presented on MHC class II proteins

Question 21

BCR vs. antibody

Answer 21

BCR is identical to Ab except that Ab’s lack the transmembrane domain that anchors the BCR in the plasma membrane

Question 22

What does an increased lymphocyte count indicate

Answer 22

Ongoing viral infection

Question 23

IgM

Answer 23

Pentamer joined at their Fc regions

First Ab produced in response to exposure to a new antigen

Neutralizes toxin or pathogen

Question 24

IgG

Answer 24

Secreted as a monomer

Major Ab class found in circulation and is produced many years after antigen exposure

IgG is also transported into tissue spaces

Neutralizes, promotes phagocytosis (opsonization)

Question 25

IgA

Answer 25

Major Ab found in breast milk, colostrum, and mucosal secretions Important for neutralizing mucosal pathogens and toxins

Question 26

Immune cells that function to eliminate extracellular parasitic infections

Answer 26

Eosinophils and basophils - circulating granulocytes Mast cells - tissue resident cells ## Footnote Particularly infections with multicellular parasites that are too bid to be phagocytosed and killed

Question 27

Pathway that is activated by cytokines/chemokines bind to their cognate receptors

Answer 27

JAK/STAT signaling is activated Induces gene expression

Question 28

Cell adhesion molecules (CAMs)

Answer 28

Receptor:ligand pairs that direct cellular movement out of circulation and into the tissues (or the opposite) as well as facilitating adherence and intercellular communication Selectins bind addressins Integrins bind ICAMs

Question 29

Selectins

Answer 29

Bind different carbs found on glycosylated membrane proteins Binding partner = addressins

Question 30

Homing/Rolling Adhesion

Answer 30

First, weak binding between **L-selectin** on a naive T lymphocyte and Gly-CAM-1 on the high endothelial venule (HEV) endothelium reduces T cell velocity and T cell rolls along the HEV wall

Question 31

Integrins

Answer 31

Heterdimeric molecules consisting of and alpha and beta chain Binding partners for integrins are often immunoglobulin superfamily cellular adhesion molecules (ICAMs)

Question 32

Tight Adhesion

Answer 32

Chemokines secreted by lymph node stromal cells bind to the endothelial lumen surface in the HEV Endothelium bound chemokine binds to the naive T cell chemokine receptor and activates T cell surface integrin **LFA-1 (αLβ2)** through a process termed "inside-out" signaling. Activated LFA-1 changes its conformation and binds very tightly to **ICAM-1** on the HEV endothelium Allows diapedesis into the underlying tissu

Question 33

A. GlyCAM-1 B. L-selectin C. MHC class I D. LFA-1

Answer 33

D. LFA-1 | LFA-1 binds tightly to ICAM-1 ## Footnote L-selectin binds to GlyCAM-1 (rolling adhesion)

Question 34

A defect in which cell type would produce the most serious immunodeficiency? A. Mast cells B. B cells C. Neutrophils D. CD8+ T cells E. Dendritic cells

Answer 34

E. Dendritic cells ## Footnote Without DCs you lose effector T cell population which regulates the immune system

Question 35

Why does IgM in newborn indicate in utero infection while positive IgG does not?

Answer 35

IgM is a pentamer and cannot pass through the placenta, therefore, any present IgM must be the newborn's