I lOVE my green smoothies! I'll have to try adding wheat grass--it's not on my ingredient list at the moment. Regarding immune boosting, I take a supplement called EBOOST every day. It's a powder that you add to water and it turns into a slightly fizzy Tang-like drink. I find it improves my focus & energy, but it also has tons of immune-building ingredients. I liked it so much that I started talking to the company and now I'm doing their social media for them. And I still drink it every day. :) Let me know if you want to try it and I'll send you some samples. Here's a blog post I wrote for them about building your immune system: http://www.eboost.com/blog/tag/immune-system/