As your immune system develops so new immune cells are created in your lymph nodes this is why we feel tenderness and swelling in our glands.

The explosive increase in the number of lymphocytes, both B cells and T cells, from just a few to millions in the presence of an infection was discovered in the 1950s. The process, called clonal expansion, is what gives the adaptive immune system its extraordinary might and specificity. You can tell that clonal expansion is occurring when you feel tender bumps (swollen lymph nodes) in your neck or other areas.

When lymphocytes multiply during clonal expansion, some of them are destined to live on as memory T and B cells. These clones are a subset of the expanded number of T and B cells that develop from your first exposure to a germ, and they protect you against subsequent attacks by the same germ.

Because of this new population of memory cells, the responses to subsequent attacks are faster and greater than the first. This explains why once you've had an infectious illness, you don't get sick when you're exposed to it the next time around - Immunological memory

Feeding your immune cells

The immune system consists of a finely orchestrated, complex collection of tissues and cells that protect your body from allergens, bacteria, viruses, and other potentially harmful organisms, collectively known as antigens. 

Skin and the membranes that line entrances to the body -- nasal passages, eyes, and respiratory and digestive tracts -- are the first line of defence, providing a physical barrier against invaders. 

Internally, specialized white blood cells fight antigens that make it past the skin: T-lymphocytes continuously patrol the body in search of antigens; B-lymphocytes manufacture antibodies, special blood proteins that neutralize or destroy germs.

Neutrophils and macrophages scavenge antigens from the blood for delivery to the lymphatic system, which disposes of them. To work smoothly, these cells depend on you feeding them

This is what your immune cells need:

selenium which helps white blood cells produce the proteins they need to clear out viruses. 

zinc (pumpkin seeds)which is important in the development of white blood cells. 

vitamin A, a component of healthy skin. The skin is the first line of defense against infection. Vitamin A is also important to T-Cells and natural killer cells

glutamine, an amino acid that is used by immune cells during times of stress, inflammation, and infection, especially by lymphocytes, macrophages, and neutrophils. 

glutathione, an antioxidant that strengthens the immune system

allicin, which fights bacterial infections and cancer 

beta glucan (PGG glucan) that enhances the function of macrophages and neutrophils.