Question

Please do it soon.

4. a. We discussed leukocyte extravagation. How does the white blood cell of a patient know there is an infection nearby? The white cells will detect unfamiliar structures of the bacteria and consider it foreign. Ourbody will increase phagocytosis. It helps attack the bacteria. And destroys other cells. b. In another patient, assume cells in the trachea and upper respiratory regions of the lungs have a Covid-19 infection. White blood cells are needed there. Speculate how might white blood cells know there is a viral infection there (remember a virus does not have many proteins (a coat, RNA directed RNA polymerase, and 3-4 other proteins)? The white blood cells will find a foreign cells such as the bacteria in the lungs

Answer 1

4a. The white blood cells or the leukocytes which travel around inside the body to the tissues through blood as medium. When there is an infection the infected cells secrete chemokines like IL1 and TNFalpha which attracts the white blood cells to site and there the white blood cells especially the neutrophils carry out phagocytosis to eliminate the pathogen or foreign body.

b.

The virally infected cells will produce proteins with parts of the viral peptide expressed in it and send it out to the surface of the cell where major histocompatability complexes binds these antigens(viral peptides) on the cell surface. The T cells a type of white blood cells which are circulating in the blood recognise the MHC bound cells through their T cell receptors, this inturn binds with the MHC molecules and elicits a defence reaction known as complement cascade and cytokines which are cytotoxic agents within the T cell. Then these cytotoxic agents kill the infected cells.This is how the white blood cells know the site of infection and travel to that site and carry out immunological defence.