Morphological and immunofenotypic features of the monoclonal population of B-lymphocytes in chronic lymphocytic leukemia

Purpose of the study. To evaluate the features of morphological and immunophenotypic characteristics of the lymphoid population with different restriction of light chains of immunoglobulins in patients with chronic lymphocytic leukemia (CLL).Materials and methods. The study included 30 CLL patients aged 47–79 years (20 men and 10 women). All patients underwent a General clinical blood test (SysmexXE 2100, Japan), morphological examination of the bone marrow (BioVision; Micros, Austria), immunophenotyping of bone marrow and peripheral blood by flow cytofluorometry (Navios10/3, Beckman Coulter, USA). B-cell clonality established by detection of restriction of light chains of surface immunoglobulins kappa or lambda. Morphological analysis of lymphocytes that differ in the expression of light chains of surface immunoglobulins: kappa (k) — group I (22 people — 73,3%), lambda (λ) — group II (8 people — 26,7%).Results. Determination of cell types by values of direct (FSC) and lateral (SSC) light scattering during immunophenotyping of peripheral blood and bone marrow samples showed that in patients of group I (CD19k+/CD5+/CD23+) on the light scattering diagram, the lymphoid population had low parameters: on the FSC scale — from 200 to 400, on the SSC — from 10 to 160 units, which indicates morphological uniformity of cells. In group II (CD19λ+/CD5+/CD23+), on the contrary, on the light scattering sketogram, the lymphoid zone was heterogeneous and stretched: on the FSC scale — from 200 to 1000, on the SSC — from 10 to 400 units, which indicates morphological polymorphism of cells. There were also differences in the expression of the common leukocyte antigen CD45. In group I, the expression is higher: the population of B-lymphocytes in terms of fluorescence intensity is on the dot graph on the CD45 scale in the second half of the third decade and in the fourth decade — to the right, than in group II, in which B-lymphocytes lie in the third decade. The data indicate that the CD19k+/CD5+/CD23+ population is represented by Mature cells, while the Cd19k+/CD5+/CD23+ population is represented by less Mature and / or intermediate forms. Significant morphological differences in lymphocyte populations were also observed in microscopic studies of blood and bone marrow preparations.Conclusion. The established immunophenotypic and morphological differences in lymphoid populations expressing either kappa — or lambda-light chains of immunoglobulins may be important for identifying risk groups among patients with biologically heterogeneous variants of chronic lymphocytic leukemia.

Immunohistochemical study of expression of immunoglobulins in canine B-cell lymphomas

Immunohistochemical study of expression of immunoglobulins in canine B-cell lymphomasNineteen canine lymphomas were included in this study. Tumors were classified according to the updated Kiel classification adapted for canine lymphomas by Fournel-Fleury et al. Immunoglobulin light chains (κ and λ) and IgM and IgG expression were determined by immunohistochemical method. In all examined cases neoplastic cells were positive for one of the immunoglobulin light chains. Expression of λ light chains and κ light chains was observed in 18/19 and 1/19 tumors, respectively. In the majority of neoplastic cells in each examined specimen this reaction had a membranous pattern (sκ/sλ). In all examined cases the presence of immunoglobulin light chains was also observed in the cytoplasm of some neoplastic cells (cκ/cλ). These cells were usally rare and never constituted a dominant population. The expression of immunoglobulin was found in 13/19 cases. Most lymphomas were sIgM positive (11/13 cases). In one case expression of IgG was found, and in another lymphoma two populations of neoplastic cells with different expression of examined immunoglobulins (cells with IgM+and IgG+phenotypes) were observed. The reaction also had a membranous pattern. The cells containing cytoplasmic immunoglobulins were rare, and in most cases were of the same type as the surface immunoglobulins. Our study has confirmed that canine lymphomas are a monoclonal proliferation of B-cells usually expressing immunoglobulin λ light chains and that the vast majority of tumors deriving from B-cells express IgM. Our study also indicates a possibility of occurence of biclonal lymphomas in canine species.

The VP6 Protein of Rotavirus Interacts with a Large Fraction of Human Naive B Cells via Surface Immunoglobulins

ABSTRACT Immunity to human group A rotavirus (RV), a major cause of viral gastroenteritis in infants, involves B lymphocytes that provide RV-specific antibodies. Additionally, some arguments suggest that naive B cells could be implicated in the first steps of the immune response against RV. The aim of our study was to analyze the interaction of VP6 and VP7 RV capsid proteins with human B cells depending on the immune status of the individual, i.e., naive or RV experienced. For this purpose, a two-color virus-like particle flow cytometry assay was devised to evaluate the blood B-lymphocyte reactivity to VP6 and VP7 proteins from healthy RV-exposed adults, recently infected infants, and neonates at birth. Both VP6 and VP7 interactions with B cells were mediated by surface immunoglobulins and probably by their Fab portions. VP7-reactive B lymphocytes were mainly detected from RV-experienced patients and almost exclusively in the CD27-positive memory cell fraction. Conversely, VP6-reactive B lymphocytes were detected at similar and high frequencies in adult, infant, and neonate samples. In adult samples, VP6 reacted with about 2% of the CD27-negative (CD27neg) naive B cells. These results demonstrated that the VP6 RV protein interacted with a large fraction of naive B lymphocytes from both adults and neonates. We propose that naive B cell-VP6 interaction might influence the strength and quality of the acquired immune response and should be considered for elaborating RV vaccine strategies.

CD5 is a potential selecting ligand for B cell surface immunoglobulin framework region sequences.

In rabbits nearly all B lymphocytes express the glycoprotein CD5, in contrast to mice and humans, where only a small proportion of B cells express this molecule (Raman, C., and K.L. Knight. 1992. J. Immunol. 149:3858-3864). CD5+ B cells appear to develop early in ontogeny and be maintained throughout life by self-renewal. The function of CD5 on B cells is still unknown. We showed earlier that "positive" selection occurs during B lymphocyte development in the rabbit appendix. This selection favors B cell expressing surface immunoglobulins with VHa2 structures in the first and third framework regions (Pospisil, R., G.O. Young-Cooper, and R.G. Mage. 1995. Proc. Natl. Acad. Sci. USA. 92:6961-6965). Here we report that F(ab')2 fragments, especially those bearing VHa2 framework region determinants, specifically interact with the B cell-surface glycoprotein CD5. This interaction can be inhibited by anti-CD5 antibodies. Furthermore, immobilized F(ab')2 fragments selectively bind CD5 molecules in appendix cell lysates. Interactions of VH framework region structures with CD5 may affect maintenance and selective expansion of particular B cells and thus contribute to autostimulatory growth of autoimmune or transformed cells.