During immunophenotyping experiments we came across a strange blood sample of a clinically healthy subject which lacked CD16 signal on neutrophils. Blood samples of other subjects had with the same antibody (clone 3G8) normal signal. Monocytes and NK cells of the above mentioned atypical blood were detected by this antibody normally. Neutrophils themselves were present in this blood and staining pattern of CD15 and CD24 on them was also normal. To examine whether this phenomenon was epitope-dependent we repeated the experiment with two other anti-CD16 clones, namely LNK16 and MEM-154. The results revealed that epitope-related polymorphism was not involved, but the atypical blood donor did not express CD16b on granulocytes, while expression of CD16a on monocytes and NK cells was not affected. CD16b is a GPI-anchored antigen, but the subject was not suffering from PNH (paroxysmal nocturnal hemoglobinuria; there is a lack of GPI anchor synthesis in such patients), so there had to be a defect in CD16b expression here.
In the literature we found that this phenomenon globally concerns ~1/2000 people, but with substantial local differences. Nagarajan et al. 2000 identified a blood donor with no CD16b expression (caused by a genetic defect), where functions of CD16b were partially compensated by CD32a, another low affinity receptor for monomeric IgG with similar functions to that of CD16. However, some neutrophil functions were significantly reduced in CD16b deficient donor. Similarly, Riera et al. 2009 observed CD16b null phenotype in neutrophils of two non-PNH patients. Also Golay et al. 2019 described a donor completely lacking CD16b protein and RNA expression and analysed the differences between neutrophil functions of this subject and the wild type. Minguela et al. 2021 focused on incidence of CD16b null phenotype among patients with blood and immune system disorders and their data indicate there might be a prognostic relevance of this feature regarding progression of myeloid neoplasms.
Naturally occurring CD16b deficiency seems to be an interesting tool to understand the functions of various IgG receptors in the immune system and to learn more about subtle modulations of neutrophil effector functions. It can also have a prognostic importance concerning hematological malignancies. We came across with CD16b null blood by chance during another experiments and were not able to use it for thorough research, but you may find it in a targeted way, allowing you to utilize fully its scientific potential.
Fig. 1: The atypical blood donor did not express CD16b on granulocytes, whereas expression of CD16a on monocytes and NK cells was not affected compared to a normal blood donor.
Fig. 2: The atypical blood with CD16b null phenotype did not lack classical granulocyte markers (except from CD16b), as confirmed using CD24 staining (which is also a GPI anchored protein, thus PNH was excluded even this way) and CD15 staining. Concerning CD16, we observed the same pattern with clones LNK16 and 3G8, demonstrating that the phenomenon is not epitope-dependent. Interestingly, another anti-CD16 clone MEM-154, which depends on presence of 158V polymorphism in CD16a isoform, lacked signal also on CD16a-expressing populations, indicating that both CD16b null donor and the normal blood donor had 158F polymorphism on CD16a in this experiment.
Nagarajan S, Venkiteswaran K, Anderson M, Sayed U, Zhu C, Selvaraj P: Cell-specific, activation-dependent regulation of neutrophil CD32A ligand-binding function. Blood 2000, 95(3):1069-1077.
Riera NE, Rosso Salto M, Canalejo K, Felippo ME, Arrossagaray G, Aixala M, de Bracco MM: Ausencia del receptor CD16b en neutrofilos. Medicina (Buenos Aires) 2009, 69:442-446.
Golay J, Valgardsdottir R, Musaraj G, Giupponi D, Spinelli O, Introna M: Human neutrophils express low levels of FcγRIIIA, which plays a role in PMN activation. Blood 2019, 133(13):1395-1405.
Minguela A, Salido EJ, Soto-Ramirez MF, Montes-Ares O, Leal JD, Garcia-Garay MC, Periago A, Berenguer M, Blanque M, Campillo JA: Low-affinity immunoglobulin gamma Fc region receptor III-B (FcγRIIIB, CD16B) deficiency in patients with blood and immune system disorders. Br. J. Haemat. 2021, 195:743-747.
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