Cutaneous immunity not reflective of systemic immunity in elderly

Philadelphia - As the human body ages, its ability to muster a robust and effective immune response diminishes, a fact reflected in cutaneous immunity.

This process can be well demonstrated when observing the rate of increased infections seen in the elderly. In skin tests, the cutaneous response to the injection of antigens is used to assess cell-mediated immunity to infections such as tuberculosis.

To ascertain if a strong cutaneous immune reaction corresponds with strong systemic immunity in the elderly, skin responses to an antigenic challenge in the elderly are analyzed. It's then determined if these cutaneous responses are reflective of an impaired systemic immunity.

Study specifics

In the study, Dr. Lacy and her team of researchers took candida and tuberculin purified protein derivative (PPD) antigens and injected them intradermally into the forearm of 25 healthy individuals under 40 years of age and 42 individuals more than 70 years of age, and assessed the clinical response.

Following the study scheme, the physician induced suction blisters over the site of injection and isolated the CD4+ T lymphocytes found in both blister fluid and peripheral blood mononuclear cells. The peripheral blood cells and the blister CD4+ T cell lymphocytes were then stained for CD69 and Ki67 in order to assess the cellular activation and proliferation respectively. Antigenic specificity was assessed by measuring and quantifying interferon-alpha production after an overnight stimulation with the antigens. The proliferation of the peripheral blood mononuclear cells was also measured after five days in culture with the antigens, as well as the concentration of cytokines within the blister fluid. Additionally, the skin homing capacity of CD4+ T cell lymphocytes in the blood was assessed by staining for cutaneous lymphocyte antigen (CLA) and chemokine ‹c-c motif› receptor four (CCR4).

Skin response reduced in elderly

Results demonstrated that the clinical response in the skin following antigen injection was significantly reduced in the elderly individuals compared with the younger group (p=0.0001).

Dr. Lacy noticed that in the young study participants, the peripheral blood mononuclear cell response correlated well with the clinical response - specifically speaking, the measured degree of cellular proliferation as well as the number of antigen specific cells at the site of injection. The cutaneous lymphocyte antigen and CCR4 expression on antigen specific peripheral blood mononuclear cells was found to be the same in the young as well as the elderly study participants, suggesting a skin specific defect. Also, a reduction in tumor necrosis factor (TNF), monocyte chemotactic protein-1 (MCP-1) and monocyte chemotactic protein 1 alpha (MCP 1 alpha) levels were observed in the blister fluid of the elderly individuals.

Dr. Lacy says that this finding may be associated with the defective migration of T cells into the skin following an antigenic challenge.

Dr. Lacy tells Dermatology Times, "In spite of the good peripheral blood mononuclear cellular response in our elderly study participants, there was a significant absence of a clinical as well as cellular response in their skin. This clearly proves that there is a disassociation between systemic and cutaneous immune responses in elderly individuals. This finding has important implications for the use of skin testing to assess immunity."

Dr. Lacy hypothesized that this skin-specific reduction in immunity with age may well partially account for the increase in cutaneous malignancies and infections so often witnessed in elderly patients.