Immune Cells Get Together In The Lung Of Patients With Rheumatoid Arthritis (Medical News Today) Cells of the immune system congregate at various sites throughout the body, and it is at these sites that they become primed to respond to invading microbes. Although in some species immune cell congregates can be found in the airways of the lung at all times, most healthy humans lack these congregates (which in the lung are known as bronchus-associated lymphoid tissues (BALT). [click link for