Question

1) You are exposed to influenza viruses, and alas, you have not yet had your influenza vaccine this year! Unfortunately, the viruses manage to bind successfully to epithelial cells in your nasal passageways, initiating an infection.

a) Follow the pathway of a single virus as it initiates its infection, resulting in the production of numerous virus particles.

b) Describe your immune system and its response: both innate (first line, that was breached, and second line of defense) and adaptive. Which components may not have played a role in protecting you, and which ones will ultimately hopefully clear this infection?

2) Consider a group of humans all exposed to pathogens (i.e., the same disease-causing organism, but presumably a population of such!) Examples might be a group of people eating at a restaurant, or all exposed to a respiratory pathogen in a shopping mall, classroom, or on an airplane, etc.

a) Would everyone come down with the illness? Why or why not?

b) If not, how would you explain the variability in response in terms of 1) differences attributable to pathogens and 2) differences attributable to humans?

Answer 1

1a) The virus attaches itself to the epithelial cell membrane in the nasal passage and it injects its genetic material (DNA or RNA) into the host cell (epithelial cell). It uses the host cell machinery to produce new virus particles and when all the parts of the virus are assembled, it ruptures the host cell and release new viruses into the body via circulation.

1b) The first line of defense present in the nasal passages are the mucus secretions, cilia and hair where the mucus secretions restrict the entry of virus into the body or attachment to cell membrane. When the first line of defense failed, second line of defense takes its action which includes macrophages and other phagocytic cells. These cells can identify the foreign or pathogenic cells invading the human body and it engulf such cells and degrade it to small pieces. This phagocytic action is second line of defense mechanism for innate immunity.

The adaptive immunity is to protect the body quickly when the same virus enters in the future. The antigen presenting cells like macrophages which degrade the pathogens into pieces process and present this to the T cells. And, T cells activate B cells to produce antibodies specific to pathogen and also activate other T cells to produce cytokines.

Therefore, first line of defense failed and thats why the virus could initiate an infection but the second line of defense could clear the infection.