It is now well established that human ageing is accompanied by an increase in systemic, low-grade (chronic) inflammation, sometimes termed inflammaging (Franceschi, 2007). This is in part due to more global changes to the body, including an increased number of senescent cells, but of interest to me currently is the change in the composition of the circulating immune cell sub-types that may either cause, or be affected by, the increase in 'global' inflammation.
I imagine the answer to this question is a study that samples individuals of different ages and separates the various leukocyte fractions. Using this it could be determined which immune sub-types are over-/under-represented in the aged, and at what age the changes occur (e.g. monocyte numbers may decrease from age 40, whereas neutrophil numbers may increase...). I have done some fairly extensive research, but have been unable to find a study that has done this - however it seems likely that it has been performed. Thanks.