Question

Discuss the general measures taken by the innate and adaptive immune cells in response to a virus.

What are type III hypersensitivities, and how are they induced; additionally, why are they the hardest to diagnose in a patient

Answer 1

Solution

• After infection Viruses initially activate the innate immune system, which recognizes viral components through pattern-recognition receptors (PRRs).
• pattern recognition receptors (PRRs) are engaged to detect specific viral components such as viral RNA or DNA or viral intermediate products and to induce type I interferons (IFNs) and other pro-inflammatory cytokines in the infected cells and other immune cells

• In adaptive immune system-class I major histocompatibility complex proteins (or MHC class I, for short) to display pieces of protein from inside the cell upon the cell surface. If the cell is infected with a virus, these pieces of peptide will include fragments of proteins made by the virus.

• A special cell of the immune system called a T cell circulates looking for infections. One type of T cell is called a cytotoxic T cell because it kills cells that are infected with viruses with toxic mediators.

• The Cytotoxic T cells have specialised proteins on their surface that help them to recognise virally-infected cells. These proteins are called T cell receptors (TCRs).

• Each cytotoxic T cell has a T cell receptor that can specifically recognise a particular antigenic peptide bound to an MHC molecule. If the T cell receptor detects a peptide from a virus, it warns its T cell of an infection.

• T cell releases cytotoxic factors to kill the infected cell and, therefore, prevent survival of the invading virus in the body.

Type III Hypersensitivity-

• This is a immune reaction occurs through the formation of antigen-antibody complexes that activate complement and result in tissue damage.
• This damaging inflammatory reaction is triggered by a soluble antigen capable of forming large insoluble immune complexes (IC) with IgM or IgG antibodies in the circulation of blood.

The type III hypersensitivity reactions immune-complex deposition (ICD) causes autoimmune diseases, which is often a complication for diagnosis.

Because as the disease progresses a more accumulation of immune-complexes occurs, and when the body becomes overloaded the complexes are deposited in the tissues and cause inflammation as the mononuclear phagocytes, erythrocytes, and complement system fail to remove immune complexes from the blood thatwhy its hard to diagnose type III hypersensitivity reaction.