Selenium and Zinc are essential for a functioning immune system. They become depleted in chronic infections. Also, prior to starting medication i think it is quite important to adjust to low inflammation diet (no sugar, no gluten, light meat, lots of veggies, organic stuff, goat dairy, plenty of water, lemon). Anything that is anti-inflammatory, when you have a chronic infection, can be seen as immune booster. Inflammation is the way the body signals the need for immune attack. So if you have an inflammation from non-infection factors, like for eg gluten , your body's immune system will get confused and a confused army cannot see the real enemy and starts shooting down the trees instead..
That and some vitamins are IMHO the best preps. Don't take huge doses of B6 without checking your blood levels ! Anything above 10mg/day on long term may have toxic effects on your nerves and the sad thing is lyme toxins do the same thing to your nerves, so you will not know if you herx or got intoxicated with b6...
That being said, herbals are IMHO most of the time used as immune system boosters, so i see cat's claw as immune support
For adrenals i used Ashwagandha with great results, but if you've read my earlier thread, one has to be careful with the dosage. Later in treatment when your body gets in a better shape, you need to discontinue it or it will drive you into over-adrenaline/over-thyroid mode. I remember i felt as if i took amphetamines, it was 3am in the morning and i felt like running around the building ...