Intro to Immuno Flashcards
Primary lymphoid tissue
Bone marrow and thymus
Secondary lymphoid tissues
Sites where T and B lymphocytes first contact antigens
Lymph nodes, spleen, and mucosal associated lymphoid tissues (MALT)
Polymorphonuclear leukocytes
aka granulocytes:
Neutrophils
Basophils
Eosinophils
Develop from the myeloid lineage in the bone marrow
BCR vs. TCR
Primary role of innate immune response
Resist initial infection
Induce local inflammation
Faciliatate adaptive response
Promote wound healing
Adaptive immune response against extracellular pathogens
Humoral immunity
(Ab’s cannot penetrate intact cells, so ineffective for intracellular paths)
Cell-mediated immunity
Primarily mediated by T cells
TCR’s bind antigen-MHC complex
Important defense against both extracellular and intracellular pathogens
CD8+ cells
Kill pathogen-infected cells
Only recognize antigen peptides presented on MHC class I proteins (intracellular pathogens)
Cells involved in innate immune response
NK cells
Neutrophils
Macrophages
Dendritic cells
NK cells
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
Neutrophils
Circulating WBCs that migrate into sites of tissue infection
Phagocytose and kill ectracellular microbial pathogens and stimulate wound healing after infection is eradicated
Macrophages
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
Waldeyer’s ring
What secondary lymphoid tissues helps detect systemic infections
The spleen
What MALTs protect the respiratory and GI tract entrance?
The adenoids and tonsils
Microfold cells (M cells)
Specialized epithelial cells that deliver antigen across epithelial cell barrier to the underlying MALT
First step in activating the adaptive immune response
Activation of pathogenantigen responsive naïve T cells by dendritic cells in 2° lymphoid tissues
Takes roughly 3-4 days
What cells initiate the adaptive immune response?
Dendritic cells
What stimulates immature DCs to mature?
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
CD4+ cells
Helper or regulatory T cells
Recognize antigen peptides presented on MHC class II proteins
BCR vs. antibody
BCR is identical to Ab except that Ab’s lack the transmembrane domain that anchors the BCR in the plasma membrane
What does an increased lymphocyte count indicate
Ongoing viral infection
IgM
Pentamer joined at their Fc regions
First Ab produced in response to exposure to a new antigen
Neutralizes toxin or pathogen
IgG
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)
IgA
Major Ab found in breast milk, colostrum, and mucosal secretions
Important for neutralizing mucosal pathogens and toxins
Immune cells that function to eliminate extracellular parasitic infections
Eosinophils and basophils - circulating granulocytes
Mast cells - tissue resident cells
Particularly infections with multicellular parasites that are too bid to be phagocytosed and killed
Pathway that is activated by cytokines/chemokines bind to their cognate receptors
JAK/STAT signaling is activated
Induces gene expression
Cell adhesion molecules (CAMs)
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
Selectins
Bind different carbs found on glycosylated membrane proteins
Binding partner = addressins
Homing/Rolling Adhesion
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
Integrins
Heterdimeric molecules consisting of and alpha and beta chain
Binding partners for integrins are often immunoglobulin superfamily cellular adhesion molecules (ICAMs)
Tight Adhesion
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
A. GlyCAM-1
B. L-selectin
C. MHC class I
D. LFA-1
D. LFA-1
LFA-1 binds tightly to ICAM-1
L-selectin binds to GlyCAM-1 (rolling adhesion)
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
E. Dendritic cells
Without DCs you lose effector T cell population which regulates the immune system
Why does IgM in newborn indicate in utero infection while positive IgG does not?
IgM is a pentamer and cannot pass through the placenta, therefore, any present IgM must be the newborn’s
