Human peripheral basophils extended phenotype shows a high expression of CD244 immuno-regulatory receptor.

Introduction: Basophils play a major physio-pathological role in hypersensitivity related diseases. Basophils express high affinity Immunoglobulin (Ig) E receptors (FcεRI), IgG and complement regulatory. Basophils also have immunoregulatory activity through interaction with T cells. The aim of this study was to look for the expression of markers reflecting the activation status of peripheral Basophil in healthy donors.

Method: the study was performed on 29 healthy donors, 62% females with a mean age of 50.1 + 17.0 years. Basophils were identified on their expression of CD123 without HLA-DR and/or CD193 in two 8 colors panels including CD46, CD55, CD59, CD203c, CD32 (FcγRII), CD64 (FcγRIII), CD163, CD137L (4-1BBL), CD252 (OX40L), CD244 (2B4) and CD3 on whole blood. Basophil activation with anti IgE was performed on 14 donors.

Results And Discussion: Our results confirmed the Basophil expression of CD123, CD193 and CD203 (the latter is strongly increased under stimulation). Complement regulatory proteins (CD46, CD55, CD59) were expressed at the same levels as on other leukocytes; CD46, CD59 expression being slightly increased under stimulation. CD32 and CD163 scavenger were slightly higher than on lympho and not influenced by activation. CD252 or CD137L were expressed at low levels and significantly induced by stimulation. Most of all, CD244 was highly expressed on Basophils as compared to any other leukocytes in fresh peripheral blood.

Conclusions: Our study shows that human resting Basophils express IgE and IgG Fc receptors and check point receptor CD244 that could potentially play a role in their previously reported immunoregulatory activity in sensitization and even in tumor immune escape.