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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.

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From my Immunology notes:

*Decrease in hematopoietic stem cells resulting in a reduction of Affector cells. Erythroid and myeloid progeny cells don't seem to be affected.

*Fewer pro-B cells, resulting in fewer affector B-cells.

*Lymphoid progenitors in the bone marrow and thymus mature.

*Lymphocytes in secondary lymphoid organs.

For the Innate system:

*Neutrophils have a reduced capacity for Oxidative bursts, Batericidal activity, and Chemotaxis.

*Macrophages have a reduced capacity for phagocytic activity, oxidative bursts, and MHC II expression (which impairs their ability to present antigen and initiate CD4 Helper T-Cell responses).

*NK Cells have a reduced capacity for Cytotoxicity, proinflammatory cytokines and chemokines,and proliferation in response to IL-2. However, the total number of NK cells increases.

The sources: Both clinical (it was at a teaching hospital) and Aging and Immune System, Chapter 33 of the class text: Cellular and Molecular Immunology

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Does the textbook give any information on the different stages of the decline? I.e. at what ages the various changes occur, whether the adaptive immune response is affected more-so? Thanks for the answer though - will have a look for that chapter. –  Luke Aug 16 '12 at 9:35
    
30 and 60 were the major milestones mentioned in my notes, where an increased prevalence of cancers and diseases (respectively) become significant. However, that's probably due to the architecture of the studies the authors drew the numbers from and not any natural impetus. My personal guess would be that after 30 it's just a downward sigmoidal curve without any "hard" ages that signify major shifts in immunological makeup. –  MCM Aug 16 '12 at 14:10

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