High Incidence of Ancestral HLA Haplotype 8.1 and Incomplete DH-JH Immunoglobulin Rearrangement in Persistent Polyclonal B-Cell Lymphocytosis.

Abstract

Four women aged from 48 to 51 years with persistent polyclonal B-cell lymphocytosis (PPBCL) were studied for the clonality of B-cell population and HLA haplotype. All patients were smokers, one presented an immune deficiency syndrome due to decreased IgG and IgA levels, the others were asymptomatic. All patients presented serum increase of polyclonal IgM (5.55 – 8.12 g/L), absolute peripheral lymphocytosis ranging from 6100 to 10500/μL with elevated proportion of B cells, the percentage of CD5/CD19 lymphocytes < 5%, and binucleated/bilobulated lymphocytes accounting for 5–9% of nucleated cells on the blood smear. In one patient, cytogenetic study revealed trisomy 3 in 4 out of 40 metaphases, +18 in 2 cells, and i(18q), +15, t(13,14) in single cells. In the remaining patients no clonal chromosomal abnormalities were found. All patients were HLA typed by PCR based sequence specific primer amplification. HLA allele and haplotype incidence in patients' group were compared to healthy population of 286 ethnically matched (Caucasian, Polish) controls. DRB1*07 allele was found in 2/4 patients, seems than to be elevated than in general Polish population but a small number of patients does not allow to perform relevant statistical tests. Moreover we found significantly more frequent B*08-DRB1*03 fragment of ancestral HLA 8.1 haplotype (8.1 AH) in PPBCL patients (3/4) than in control group (47/286) (OR=15.3; 95% CI 1.55–150; p=0.02). Peripheral blood mononuclear cells from all PPBCL patients were also studied for monoclonality in immunoglobulin (IGH VH-JH, incomplete DH-JH, IGK, IGL) and crosslineage TCR (TCRB, TCRG, TCRD) genes rearrangements according to BIOMED-2 protocol. The multiplex PCR reactions were followed with heteroduplex analysis of PCR products. We found polyclonality of lymphocytes population in all tests except incomplete DH7-JH IGH rearrangements in 2 patients. The described gene rearrangement was not related to other upstream DH or downstream JH gene segments. The HLA incidence we found is distinct from previously described elevated incidence HLA DRB1*07 allele and may suggest another genetic background of PPBCL pathogenesis. Moreover, our finding of high prevalence of 8.1 AH, known to be more frequent in autoimmune diseases, and to worsen the prognosis in some infectious diseases and non-Hodgkin lymphomas, as well as of the incomplete DJ monoclonality in 2/4 patients, warrant further studies aiming to determine the relationship between PPBCL, immune disorders and true lymphoproliferative diseases.