Reduced frequency of peripheral dendritic cells in type 2 diabetes

It is a common clinical experience that type 2 diabetic patients are susceptible to opportunistic infections. The underlying reasons for this immune deficiency are not yet understood. Dendritic cells (DC) play a key role in initiating innate and adapted immune responses.

In order to investigate changes in the DC compartment in the peripheral blood in type 2 diabetes, we analyzed blood from patients under poor and good metabolic control and compared them to healthy controls.

5 mls of blood were collected from 15 healthy controls, 15 diabetic patients with an HbA1c <7.0 and 15 patients with an HbA1c >9.5%. Age range was 44-80 years. Patients were age-matched with the control group.

Blood DC were enumerated by flow cytometry after staining with antibodies against the blood dendritic cells antigens 1-3 (BDCA 1-3). This allows quantification of the DC subtypes: myeloid dendritic cells type 1 (mDC1, mDC2) and plasmacytoid dendritic cells (pDC).

The relative and absolute frequency for both mDC1 and pDC was clearly diminished in patients with poor metabolic control as compared to healthy controls. In patients with good metabolic control the reduction of DC was less pronounced but still significant, particularly for mDC1.

Hyperglycemic metabolism does affect the pool of peripheral DCs and leads to a reduction of both, mDC1 and pDC. Even patients considered to be under good metabolic control appear to have a reduced peripheral pool of DC.