Innate Immunity Flashcards
Where are mature T cells found?
In bone marrow, lymph nodes, and spleen, after maturing in the thymus.
What are pluripotent HSCs?
Rare, making up 0.05% of bone marrow cells.
How can HSCs be mobilized?
From bone marrow to blood for stem cell transplants.
What happens to macrophages after activation?
They increase MHC class I & II expression.
Where do T cells and B cells develop?
T cells in thymus, B cells in bone marrow and spleen.
Where are lymphoid follicles found?
In secondary lymphoid tissues, including MALT.
What stimulates infection and inflammation?
Cytokine and chemokine release to boost myeloid lineage development.
What do FDCs present to B cells?
Soluble antigen.
From which precursors can dendritic cells arise?
Both myeloid and lymphoid precursors.
What do B and T lymphocytes have?
Antigen-specific receptors, unlike NK cells.
Where are B cells generated in birds and ruminants?
Outside bone marrow.
What do myeloid cells include?
Dendritic cells, neutrophils, basophils, and macrophages.
What do lymphoid cells include?
NK cells, T cells, B cells, and ILCs.
What are secondary lymphoid organs?
Lymph nodes, spleen, and MALT.
What are primary lymphoid organs?
Bone marrow and thymus.
How do HSCs differ from mature blood cells?
HSCs are multipotent and capable of self-renewal.
How does the thymus avoid autoimmune responses?
Negative selection of thymocytes that bind self-antigens with high affinity.
When is the thymus at its maximal size?
During puberty, then gradually atrophies.
What happens to immunodeficient mice in HSC enrichment?
Stem cells restore immune cells, showing successful enrichment.
What are monocytes?
Blood precursors of macrophages with limited phagocytic capacity.
How do macrophages compare to monocytes?
Larger than monocytes, with enhanced phagocytosis and cytokine secretion.
What happens after bursectomy in chickens?
Leads to lack of B cells and humoral immunity.
What is the major antigen-presenting cell for naïve T cells?
Dendritic cells.
What is the phagocytic cell in the CNS?
Microglial cells.
Which granulocytes act against parasites?
Eosinophils.
What gives rise to red blood cells?
Myeloid dendritic cells and HSCs.
What are the first cells to arrive at an inflammation site?
Neutrophils.
What maintains HSCs?
Osteoblasts.
What gives rise to thymocytes?
Hematopoietic stem cells (HSCs).
What do monocytes differentiate into?
Macrophages in tissues.
What is the antigen-presenting cell from the same precursor as T cells?
Lymphoid dendritic cells.
What samples antigen in the intestinal lumen?
M cells.
Which granulocytic cells release pharmacologically active substances?
Eosinophils, mast cells, neutrophils.
Which cells are involved in allergies?
Eosinophils and mast cells.
Which cells express antigen-specific receptors?
Lymphocytes and NKT cells.
What are cells with a common progenitor to T and B cells but no antigen receptors?
Innate lymphoid cells.
Where is NFAT located under resting conditions?
In the cytoplasm.
Where is NFAT located under activated conditions?
In the nucleus.
What causes NFAT relocalization?
Dephosphorylation by calcineurin, activated by calcium-calmodulin.
What is the effect of cyclosporin on NFAT?
Inhibits calcineurin in T cells, preventing NFAT activation.
What do immunoglobulin and TCR binding antibodies share?
Both share the immunoglobulin fold, allowing cross-reactivity.
What happens during receptor-ligand binding?
Activates the receptor, causing phosphorylation and receptor cross-linking.
What does reduction and alkylation of antibody do?
Breaks disulfide bonds and prevents reformation, allowing study of chains.
What does papain digestion of antibody produce?
Produces two Fab fragments and one Fc fragment, revealing antigen-binding sites.
How are immunoglobulin fragments detected?
Antibodies against Fab and Fc show contributions of heavy and light chains.
What is ITAM?
Immunoreceptor tyrosine-based activation motif, phosphorylated during receptor activation.
How are ITAMs in Igα and Igβ modified?
Phosphorylated by Lyn, a Src-family kinase, upon BCR activation.
What is an adapter protein?
Brings other proteins together without enzymatic activity.
What do SH2 proteins do in TCR signaling?
SH2 domains of ZAP-70 bind phosphorylated ITAMs to activate signaling pathways.
How do IgM and IgG compare in antigen-binding?
IgM binds more antigenic sites but not necessarily five times more due to steric hindrance.
What happens during cytokine receptor binding at low concentrations?
Activation may increase receptor affinity, such as with IL-2R.
How is Src-family kinase activity regulated?
Phosphorylation on inhibitory or activating sites regulates kinase activity.
What happens if Lck is inactive in a T-cell clone?
T-cell activation will not occur, preventing IL-2 secretion.
What is the protein defective in X-linked agammaglobulinemia?
Btk defects impair B-cell signaling and differentiation.
What do short BCR and TCR cytoplasmic regions do?
Signal transduction complexes (Igα/Igβ or CD3) transduce signals despite short regions.
What is the first adaptation of antibody structure?
Y-shape with flexible hinge for binding to multivalent antigens.
What is the second adaptation of antibody structure?
Variable regions with hypervariable loops to form diverse binding sites.
What is the third adaptation of antibody structure?
Constant regions enable interaction with phagocytes and complement proteins.
What happens in a constitutively active T-cell clone with Lck mutation?
Lck mutations lead to continuous activation and IL-2 secretion.
What is pleiotropy?
One molecule causing multiple effects in different cells.
What is synergy in cytokine signaling?
Two or more cytokines producing a response greater than the sum of their individual effects.
What is redundancy in cytokine signaling?
Multiple cytokines can produce the same effect.
What is antagonism in cytokine signaling?
Two cytokines causing opposite effects or inhibiting each other’s activity.
What is cascade induction?
Cytokine triggers other cytokine secretion, amplifying the immune response.
How does cytokine signaling affect lymphocyte location?
Induces expression of receptors to alter migration and retention.
What do type I interferons do?
Activate ribonucleases to degrade viral RNA, inhibiting replication.
What is the effect of defective common γ chain in immunodeficiency?
Prevents binding of multiple cytokines, impairing signaling.
