Caslon's excellent disertation is a hard act to follow. Some of what I'm going to mention is not related to the immune system but may help you recover.
One of the reasons people get recurrent colds is that the immune system does not recognize the rhinovirus (the most common cause of colds) very well. So we get recurrent infection. Another problem is that cells lining the respiratory system may take up to 4 to 6 weeks to heal if they were damaged significantly the first time around. A chest xray may take over four weeks to normalize after an episode of pneumonia even though the individual feels well. During this weakened state it is easy to catch another respiratory tract infection.
WebMD has 12 recommendations for cold. I'll mention a few
Some these have been mentioned such as yoga for relaxation
Drink Plenty of Fluids
Water flushes your system, washing out the poisons as it rehydrates you. A typical, healthy adult needs eight 8-ounce glasses of fluids each day. How can you tell if you're getting enough liquid? If the color of your urine runs close to clear, you're getting enough. If it's deep yellow, you need more fluids.
Take a Sauna
Researchers aren't clear about the exact role saunas play in prevention, but one 1989 German study found that people who steamed twice a week got half as many colds as those who didn't. One theory: When you take a sauna you inhale air hotter than 80 degrees, a temperature too hot for cold and flu viruses to survive.
Get Fresh Air
A regular dose of fresh air is important, especially in cold weather when central heating dries you out and makes your body more vulnerable to cold and flu viruses. Also, during cold weather more people stay indoors, which means more germs are circulating in crowded, dry rooms.
Do Aerobic Exercise Regularly
Aerobic exercise speeds up the heart to pump larger quantities of blood; makes you breathe faster to help transfer oxygen from your lungs to your blood; and makes you sweat once your body heats up. These exercises help increase the body's natural virus-killing cells.
You might want to try working out again in moderation
Eat Foods Containing Phytochemicals
"Phyto" means plants, and the natural chemicals in plants give the vitamins in food a supercharged boost. So put away the vitamin pill, and eat dark green, red, and yellow vegetables and fruits.
Some studies have shown that eating a daily cup of low-fat yogurt can reduce your susceptibility to colds by 25 percent. Researchers think the beneficial bacteria in yogurt may stimulate production of immune system substances that fight disease.
Statistics show that heavy smokers get more severe colds and more frequent ones.
Even being around smoke profoundly zaps the immune system. Smoke dries out your nasal passages and paralyzes cilia. These are the delicate hairs that line the mucous membranes in your nose and lungs, and with their wavy movements, sweep cold and flu viruses out of the nasal passages. Experts contend that one cigarette can paralyze cilia for as long as 30 to 40 minutes.
Is there smoke in the bar where you work?
Cut Alcohol Consumption
Heavy alcohol use suppresses the immune system in a variety of ways. Heavier drinkers are more prone to initial infections as well as secondary complications. Alcohol also dehydrates the body -- it actually takes more fluids from your system than it puts in.
If you can teach yourself to relax, you can activate your immune system on demand. There's evidence that when you put your relaxation skills into action, your interleukins -- leaders in the immune system response against cold and flu viruses -- increase in the bloodstream. Train yourself to picture an image you find pleasant or calming. Do this 30 minutes a day for several months. Keep in mind, relaxation is a learnable skill, but it is not doing nothing. People who try to relax, but are in fact bored, show no changes in blood chemicals.
Although not mentioned by WebMD, chicken soup may be helpful in treating colds..This is not a joke.
Chicken soup has been found to reduce inflammation in the respiratory system thereby lessening symptoms.
Here is the recipe for Lithuanian chicken soup from Stephen Rennard, M.D chief of pulmonary disease University of Nebraska.http://www.chetday.com/coldfluremedy.htm