Digeorge/ LOW cell 8 count

Hi, My son has been through a great ordeal and is recovering well from his Brain Damage, recent MRI suggested he has recovered nearly fully after a cardiac arrest (Tube blocking in ICU) the only issues they can see is Basil Gangalia damage and specifically around balance so not sure he will walk or when he will walk. We are waiting to see a heart specialist also as he has a vascular ring (double aortic arch) which needs surgery. Due to the discovery of the DAA they have tested for digeorge 2 weeks ago and awaiting results, they have some tests back for Calcium and they are fine, also done lympocytes and collectively the figures are fine and they progressed to do a T and B cell split, all has come back fine except something to do with a lower cell 8 count, when he said lower apparently they benchmark the reading against healthy children of a similar age. in our case a 16MO, there wasnt an exact match though for his age so they tested on an older child and it was lower in comparison to an older child. My consultant says not to worry and its not low enough to warrant intervention but its low enough to repeat the test in say a years time. has anyone got any further information on this and what cell 8 does specifically. The reason he was put in ICU in the beginning is that he got paraflu, im worried incase the reason that it affected him so bad is that his immunity is low, if that was the case surely he would need intervention now to replace the low count.