Sequential enrichment and immunocytochemical visualization of human interferon-alpha-producing cells

Area of Science:

• Immunology
• Virology
• Cell Biology

Background:

• Human peripheral mononuclear cells (PBMC) produce interferon-alpha (IFN-alpha) upon stimulation with herpes simplex virus type 1 (HSV-1).
• Identifying the specific cells responsible for IFN-alpha production has been challenging due to their low frequency in PBMC populations.

Purpose of the Study:

• To develop and optimize a protocol for enriching IFN-alpha-producing cells from human PBMC in response to HSV-1.
• To characterize the enriched cell population and overcome the limitations of low cell frequency for identification.

Main Methods:

• PBMC were fractionated using a 48% Percoll gradient to obtain low-density (LD) and high-density (HD) populations.
• LD cells underwent further depletion of monocytes, CD3+ T cells, and CD56+ natural killer (NK) cells.
• Immunocytochemistry was used to quantify IFN-alpha-producing cells and characterize their morphology.

Main Results:

• The developed protocol achieved a greater than 125-fold enrichment of IFN-alpha-producing cells.
• The CD3/CD56-depleted population showed a significant increase in IFN-alpha production (approx. 30,000 IU/ml) compared to unfractionated PBMC (30-300 IU/ml).
• The enriched cells were characterized as medium to large in diameter with specific nuclear and cytoplasmic features, and showed a fivefold enrichment for HLA-DR+ cells.

Conclusions:

• A novel enrichment protocol effectively isolates and concentrates IFN-alpha-producing cells from human PBMC stimulated by HSV-1.
• This method facilitates the identification and study of these critical immune cells, overcoming previous frequency-related barriers.
• The enriched cells possess characteristics consistent with antigen-presenting cells, highlighting their role in antiviral immune responses.