Your meds are really acting against the anit-bodies that have invaded your body. Immune boosting cold remedies do not affect these medications that are working on your antibodies. Immune boosting cold remedies contain vitamins and minerals which have no affect, whatsoever, on your immunosuppressant medications. These vitamins and minerals are said to help build your immune system against flu and cold viruses. So, even though they both talk about the immune system, they are totally unrelated in what they do. So, you are not negating one by taking the other.
You are building up your resistance to viral infections with the cold remedies. You are suppressing the production of harmful antibodies with your medication.
I hope that I've answered your question.
Peace and Blessings
Look For The Good and Praise It!