Association Between Baseline Anti-HLA (Class I and II) and Anti-MICA Antibodies and Inflammatory Cell Infiltrates in Grafted Bone After Maxillary Sinus Floor Augmentation: An Exploratory Secondary Histological Study.

(1) Background: The role of baseline humoral immunization in bone regeneration remains unclear. This study assessed the relationship between baseline serological immunization, graft type, photobiomodulation (PBM), and histological outcomes after maxillary sinus floor augmentation. (2) Methods: This exploratory secondary analysis included 20 adults undergoing lateral maxillary sinus lifting. Patients were allocated according to graft type (allogeneic or xenogeneic) and postoperative protocol (with or without adjunctive PBM). Before surgery, serum samples were analyzed for anti-HLA class I, anti-HLA class II, and anti-MICA antibodies. After approximately 6 months, bone core biopsies were collected. Histological evaluation focused on inflammatory cell infiltrates (ICI). (3) Results: Baseline antibody positivity was detected in 35.0% of patients for anti-HLA class I, 55.0% for anti-HLA class II, and 45.0% for anti-MICA. Histological findings were generally favorable. ICI scores were low, with 65.0% of samples scoring 0 and 35.0% scoring 1. A nominal positive correlation was observed between anti-HLA class I NBG ratio and ICI; however, this finding did not remain statistically significant after correction for multiple comparisons. Exploratory PBM subgroup estimates were directionally different but were based on very small subgroups and should not be interpreted as evidence of effect modification. (4) Conclusions: The findings suggest a possible hypothesis-generating link between baseline humoral sensitization and mild local inflammatory infiltrates, which requires validation in larger, prospectively powered studies with predefined histological and immunological endpoints.