Describe how the immune system of a person without AIDS would respond to the flu virus.

The immune system of our body fights against any infection and protects us. In case of an attack by flu virus (or influenza virus), the two components of our immune system: innate and adaptive immune systems, work together to protect us and cleanse the infecting viruses from our body. The innate immune system responds first to the influenza infection and adaptive immune system starts the response a little later. 

In the first stage of immune...

The immune system of our body fights against any infection and protects us. In case of an attack by flu virus (or influenza virus), the two components of our immune system: innate and adaptive immune systems, work together to protect us and cleanse the infecting viruses from our body. The innate immune system responds first to the influenza infection and adaptive immune system starts the response a little later. 

In the first stage of immune system's action, the innate immune system is activated within hours and its activity lasts for few days (3-5 days); making it the first line of body defense (against infection). The pathogen recognition receptors recognize the foreign microbes by identifying certain molecules associate with infectious agents that are not associated with a healthy body. In response to the infection, interferons are released; this causes activation of natural killer cells which destroy infected epithelial cells. 

Adaptive immune system, takes over from innate immune system after a few days and clears the body of the foreign infection. Both the humoral and cell-mediated immunity participate in the process. The humoral immunity is affected by the B-cells, while the cell-mediated immunity is affected by T-cells (CD4+ helper and CD8+ cytotoxic cells); giving us long lasting protection from specific viral strains.

This is, in nutshell, how our immune system fights off influenza infection in a healthy (HIV-negative) body. Interestingly, the flu vaccines have to be updated every year to account for changes in the flu virus (in response to selective antibody activity against prevalent viral strain).

Hope this helps.