Immune system. Your Immune system is a general term for your body's ability to fight infections. There are textbooks written on the subject as it is very complex but includes various body organs and blood cells to keep your body free from foreign invasions.
Many things. Systemic or congenital problems such as agammaglobulinema or cgd, to acquired defects such as uncontrolled diabetes or hiv/aids. Taking various sorts of medications can suppress the immune system, such as steroids or various chemotherapy drugs. Anything that suppresses bone marrow.
Plant based foods. Avoid animal based foods which contain too much saturated fat. Eat fruits and vegetables with each meal as they will provide immune boosting nutients. Eat ample amounts of proteins from sources like eggs, fish, nuts and tofu. Low fat milk is fine too. Avoid alcohol and smoking. Exercise daily for at least 30 minutes. All of the above means a healthy lifestyle so that you will have a healthy body.
Unhealthy lifestyle. Sleep deprivation, not enough rest, not enough exercise or fresh air, unhealthy foods, not enough fruits and vegetables, apart from other reasons such as certain medicines given to suppress immunity to control some conditions,
Several. Vitamin c raises hdl, lowers blood pressure, inhibits arterial plaque. Vitamin e implicated in lowering risk of cardiovascular dz (harvard study) beta carotene stimulates production of natural killer cells, macrophages and t-cell lymphocytes. Bioflavenoids protect cell membranes. Zinc increases white blood cells to fight infection. Omega 3s increase phagocyte activity.
Immune deficiency. Immune deficiencies have multiple reasons. Some people born with it. Some are acquired or induced by different medications or conditions. These topic is too broad for this post.
Stronger immunity. Your immune system is made up of many parts. To increase the immunity, make sure you are getting good anti oxidants (the weapons to fight off infections), anti-inflammatories (to decrease the inflammation), improve your GI system which supplies the nutrition by using a probiotic, make sure your hormones are balanced and a low glycemic diet.
Immune swat team. Antibodies are like folks in line at the post office studying the wanted posters. Later they spot a felon (bacteria), grab 'em by the arm & summon the complement swat team. Complement is a group of proteins circulating in extracellular fluid. The team arrives on the scene, assembles in a specific sequence & then punches holes in the bacteria killing it. Antibodies identify; complement rubs 'em out.
Immunodeficiency. Would be the result, you will be only dependent on "innate immunity" which isn't sufficient to combat repeated infections, active immunizations won't be of any help.
What would happen if your immune system didn't fight off the flu. Would it spread to your whole body and kill u or would u just be chronically sick?
It may kill you. Yes, it would spread primarily in your lungs, causing you to mount a high inflammatory response and flood your lungs with fluid. You could die and many people die of the flu every year. In fact, in 1918, before flu vaccines, more people died of the flu around the world than in all of wwi. So, yes, you would get very sick and could die.