Virus scenario Flashcards
How do host cells recognize viral infections?
Through Pattern Recognition Receptors (PRRs) like TLRs and RLRs that detect viral components (e.g., double-stranded RNA)
What cytokines do infected cells release early in the response, and what are their effects?
Interferons (IFN-α, IFN-β); they inhibit viral replication, activate NK cells, and increase MHC class I expression
What is the role of NK cells in viral infections?
NK cells kill infected cells that lack MHC I and are activated by IL-12 and IFN-γ.
What do macrophages and dendritic cells do early in the response?
They phagocytose debris, release inflammatory cytokines (TNF-α, IL-1β, IL-6), and present antigens to T cells
How are naive T cells activated by dendritic cells?
Dendritic cells present viral antigens:
On MHC I to CD8+ T cells.
On MHC II to CD4+ T cells.
What cytokines promote Th1 differentiation, and why is Th1 important in viral responses?
IL-12 and IFN-γ promote Th1 differentiation; Th1 cells secrete IFN-γ to activate macrophages and support CD8+ T cells.
How do CD8+ T cells kill infected cells?
They recognize viral peptides on MHC I and release perforin (pore formation) and granzymes (induce apoptosis).
What cytokine do CD8+ T cells secrete, and what is its function?
IFN-γ; it inhibits viral replication and recruits other immune cells.
How are B cells activated in a T-dependent manner?
B cells present antigens to CD4+ T cells, which provide “help” via CD40L and cytokines (e.g., IL-4, IL-21).
What is the role of different antibody isotypes in viral defense?
IgM: Early response, forms immune complexes.
IgG: Neutralizes virus, enhances opsonization, and activates complement.
IgA: Protects mucosal surfaces.
What happens to most effector T and B cells after the infection resolves?
They undergo apoptosis, leaving memory T and B cells for rapid response to reinfection.
Which cytokines are key in the innate response to viruses?
IFN-α, IFN-β, TNF-α, IL-1β, IL-6.
Which cytokines are involved in T cell activation and differentiation?
IL-12, IFN-γ (Th1); IL-4 (Th2); IL-2 (T cell proliferation).
What cytokines regulate the immune response to prevent overactivation?
IL-10 and TGF-β, produced by Tregs.
How is the immune response shut down after the virus is cleared?
Regulatory T cells (Tregs) secrete IL-10 and TGF-β to suppress inflammation and allow tissue repair.
