Restricted VH3 gene usage in phage-displayed Fab that are selected by intravenous immunoglobulin

Abstract

Objective T o perform a comparative analysis of 1) intravenous Ig (IVIG)–bound Fab fragments from a patient with autoimmune thrombocytopenia that had progressed to systemic lupus erythematosus (SLE) and 2) IVIG‐selected Fabs from an SLE patient without thrombocytopenia. Methods IVIG preparations have been successfully used to treat certain cases of autoimmune thrombocytopenia and SLE. Specific interactions of IVIG with the components of the immune system are not well characterized. To investigate these, we had previously cloned a large number of phage‐displayed IgG Fab fragments, derived from 3 patients with autoimmune thrombocytopenia, that were specifically bound by IVIG molecules during panning. Many of these Fabs reacted with platelets. Sequencing revealed that the most frequently used VH germline gene segments of all IVIG‐bound Fabs were 3‐23 and 3‐30/3‐30.5. One patient's autoimmune thrombocytopenia had progressed to SLE. Using the same cloning and panning procedures, we performed a comparative analysis of this patient's IVIG‐bound Fab fragments and the IVIG‐selected Fabs from an SLE patient without thrombocytopenia. Results We observed an exclusive selection of antibodies derived from 3‐23 and 3‐30/3‐30.5 germline segments. In contrast to the Fab fragments from the autoimmune thrombocytopenia patient who developed SLE, none of the IVIG‐selected Fabs from the SLE patient without thrombocytopenia bound to thrombocytes. Conclusion Our results suggest a preferential interaction of a subfraction of IVIG—representative of normal Ig repertoires—with antibodies and B cell receptors derived from these 2 gene segments. Importantly, these are the most frequently rearranged VH germline genes among human B cells. This kind of interaction is characteristic of a B cell superantigen, since light chains, antigen specificity, and the high variation in the third complementarity‐determining region 3 showed little influence on the selection of 3‐23– or 3‐30/3‐30.5–derived Fabs by IVIG. However, at least some of the contact residues on Fabs for IVIG appear to be different from those for staphylococcal protein A and human immunodeficiency virus gp 120. The IVIG‐selected Fabs may now be used to clone antibodies representative of this IVIG subfraction to study their possible regulatory influence on the B cell repertoire during normal development and disease.

Immunoglobulin VH gene analysis in gastric MALT lymphomas

“…As there are approximately 50 different functional VH fragments in the human genome that can potentially be used, 12,13 the selective usage of the VH fragments detected in Group A tumors strongly suggests that these tumors may be derived from highly restricted B cell subsets. VH3-23 and VH3-30 have been closely associated with autoimmune disease, with the former found in patients with autoimmune thrombocytopenia, 28,29 Graves' disease, 30 and Wegener's granulomatosis, 31 and the latter in patients with systemic lupus erythematosus, 29 autoimmune thrombocytopenia, 28 and Kawasaki's disease. 32 In contrast, a biased usage of particular VH fragments has been reported in chronic lymphoid leukemia (VH3-21), 14,15 splenic marginal zone lymphoma (VH1-2), 16 and salivary MALT lymphoma (VH1-69).…”

VH3 Gene Usage in Neutralizing Human Antibodies Specific for theEntamoeba histolyticaGal/GalNAc Lectin Heavy Subunit

“…However, biases in gene family usage of the heavy-chain variable region have been reported in a number of diseases. For example, restricted VH3 germ line gene usage was observed in intravenous immunoglobulin-bound Fabs from a patient with thrombocytopenia that had progressed to systemic lupus erythematosus (31). It is known that VH3 antibodies are also important for defense against a variety of bacteria (1,39,40) and viruses (2,17,20).…”

Immunomodulatory action of intravenous immunoglobulin

“…Sequencing of IVIg-binding antibodies in a small number of patients with autoimmune disorders has suggested that IVIg can act in a manner analogous to a B-cell superantigen 15 and that B cells using V H 3Á23 and V H 3Á30/3Á35 are selectively activated following IVIg therapy. 16 Dimers and higher-order aggregates of IgG in IVIg preparations have been shown to activate neutrophils via triggering of macrophages.…”