Sore throat etc on Remicade?

I've heard Remicade weakens our immune systems. Been on it for six months. Lately I have chronic sore throat, swollen glands, feel lethargic- must be fighting an infection... Any similar experiences out there? Any suggestions for how to kick it and prevent this from recurring? (I'm also on Xolair for allergic asthma, so it's possible this isn't Remicade-related...)
Thanks in advance for your thoughts.