Shin Ei Matsumoto

IL-10 augments antibody production in in Vitro immunized lymphocytes by inducing a Th2-type response and B cell maturation

An in vitro immunization (IVI) protocol enables antigen specific antibody production from L-Leucyl-L-Leucine methyl ester (LLME)-treated human peripheral blood lymphocytes (PBL) upon antigen stimulation in the presence of IL-2, IL-4, and muramyl dipeptide. In the course of our studies, we have found that IL-10 added at the antigen sensitization significantly augmented antibody production level from the LLME-treated PBL. In the present study, we tried to demonstrate the role of IL-10 in the augmentation of antibody production in an IVI protocol by clarifying the cytokine expression profiles in CD4+ and CD8+ T cells. The results showed that IL-10 skewed the Th1/Th2 balance to Th2-type responses by suppressing Th1-type cytokine production and augmenting Th2-type cytokine production in CD4+ and CD8+ T cells, as well as in CD19+ B cells. Furthermore, IL-10 augmented the expression of CD38, an antigen marker of plasma cells, on B cells, which clearly indicates that IL-10 promoted differentiation and maturation of B cells in an IVI protocol. These results indicate that IL-10 plays an important role in setting the cellular milieu to produce antibodies in an IVI protocol.

Different individual immune responses elicited by in vitro immunization

We have previously demonstrated that the addition of muramyl dipeptide (MDP), interleukin-2 (IL-2) and IL-4 effectively raises antibody production from L-Leucyl-L-leucine methyl ester (LLME)-treated human peripheral blood lymphocytes (PBLs) against specific soluble antigen when immunized in vitro. However, PBLs from individual donors were separate optimal conditions regarding concentrations for IL-2 and IL-4, which in turn required us to optimize each individual PBLs to effectively produce antigen specific human antibody by in vitro immunization. These individual differences in the requirement for IL-2 and IL-4 reflects the differences in individual immune responses against a specific soluble antigen, which can be elicited by in vitro immunization. In the present study, we investigated these individual differences in the requirement for IL-2 and IL-4 to induce antibody productionin vitro in the PBLs of 12 volunteers (9 healthy donors and 3 allergenic patients). IL-2 requirements for antibody production varied dependent upon each donor, while higher amounts of IL-4 inhibited IgM and IgG production in all of the healthy donors. However, some of the characteristic features for PBLs donated from allergenic included lowered IgM production compared to PBLs derived from healthy donors, and very high IgE production in the absence of cytokines and allergen. These results demonstrate that the sensitivity of PBLs against antigen sensitization differs between healthy donors and atopic patients, which suggests that the frequency of antigen sensitization might be reflected in differing activation states and/or differing subpopulations of lymphocytes in vivo.

A rapid and efficient strategy to generate antigen-specific human monoclonal antibody by in vitro immunization and the phage display method.

An in vitro immunization (IVI) protocol was developed for inducing antigen-specific immune responses in human peripheral blood mononuclear cells (PBMCs). After antigen sensitization of PBMCs by IVI, B cells producing antigen-specific antibody can be propagated within a week. Here, we attempted to establish a rapid, efficient strategy to obtain antigen-specific antibody by the phage display method using in vitro immunized PBMCs. Heavy and light chain variable region genes were easily amplified from these PBMCs immunized with mite extract (ME). After generating a combinatorial phage library (1.6 x 10(5) members), 4 antigen-specific clones were selected by 5 panning rounds using biotinylated antigen and streptavidin magnetic beads. Next, we combined variable region genes of these selected clones with human IgG constant region genes and produced human IgG-type antibody. Direct and competitive enzyme-linked immunosorbent assays demonstrated that the mAb 1C11 clone bound specifically to ME. We thus established a rapid, efficient method to obtain antigen-specific human antibody genes and produce human monoclonal IgG antibody using the phage antibody library generated from in vitro immunized PBMCs.

Production of Human Monoclonal Antibodies against FcεRIα by a Method Combining in Vitro Immunization with Phage Display

An in vitro immunization protocol using human peripheral blood mononuclear cells (PBMC) was developed to generate human antigen-specific antibodies. Monoclonal antibodies have great potential, and in particular, efficient acquirement of monoclonal antibodies against membrane proteins provides advantages. In this study, we tried to generate a human monoclonal antibody against the high affinity IgE receptor, FcεRIα, using a method combining in vitro immunization and phage display. Heavy and light chain variable region genes were obtained from PBMC immunized in vitro with FcεRIα-expressed KU812F cells. Subsequently a combined phage antibody library 6×103 in the size was generated. Antigen-specific phage antibody clones were selected by panning with recombinant FcεRIα and recombined to produce human IgG format antibodies using CHO cells. The antibodies exhibited specific binding against FcεRIα. These results suggest that one can obtain membrane protein-specific human monoclonal antibodies from a relatively small phage antibody library using in vitro immunized PBMCs.

In vitro immunization can elicit the expansion of diverse repertoire of B cells from peripheral blood mononuclear cells.

We previously developed an in vitro immunization (IVI) protocol of human peripheral blood mononuclear cells (PBMC) for generating antigen-specific human antibodies. In order to clarify whether IVI protocolinduces antigen-specific B cell responses in PBMC, we analyzed family gene usage and sequence of the variable region gene of immunoglobulin heavy chain (VH gene) of the antibody produced from the in vitro immunized PBMC. Sequence homology analyses of VH gene demonstrated that a larger repertoire of B cells can be sensitized with mite-extract than with cholera toxin B subunit and rice allergen. Further, antigen-specific B cells were efficiently expanded by using CpG oligodeoxynucleotide as adjuvant. These results suggest that appropriate combination of sensitizing antigen and adjuvant is primarily important for expansion of antigen-specific B cells in IVI protocol.

Anti-Peptide Antibody Production Elicited by in Vitro Immunization of Human Peripheral Blood Mononuclear Cells

Human monoclonal antibodies have great potential for use in the treatment of various diseases. We have established an in vitro immunization protocol for inducing antigen-specific antibody production from human peripheral blood mononuclear cells (PBMCs). In the in vitro immunization protocol, PBMCs are pretreated with L-leucyl-L-leucine methyl ester (LLME) to remove suppressive cells, and are sensitized and cultured with a soluble antigen in the presence of IL-2, IL-4 and muramyl dipeptide for 8 d, and then an antigen-specific antibody is produced. In this study, we examined the novel possibility of an in vitro immunization protocol, specifically, whether LLME-treated PBMCs can be sensitized with a peptide antigen to produce an anti-peptide antibody. The results indicate that antigen-specific immune responses were elicited by a peptide antigen derived from rice allergen, a cholera toxin B subunit, and TNF-α as a sensitizing antigen in in vitro immunization. These results suggest that the in vitro immunization protocol is applicable in the generation of an anti-peptide antibody against various antigens, including food allergens, foreign antigens, and self-antigens.

Generation of a Human Anti-Tumor Necrosis Factor-α Monoclonal Antibody by in Vitro Immunization with a Multiple Antigen Peptide

We developed the in vitro immunization method to induce antigen-specific immune responses in human peripheral blood mononuclear cells (PBMCs). However, when we used a peptide as sensitizing antigen, the antigen-specific immune response was found to be weak, and hence, we could not effectively obtain the antigen-specific antibody gene. In the present study, we attempted to improve the in vitro immunization method by augmenting the immune response to the peptide antigen. We used a multiple antigen peptide for sensitization. In vitro immunization of the multivalent antigen elicited a strong antigen-specific immune response in the PBMCs, and we succeeded in obtaining antigen-specific antibody genes by the phage-display method. Further, by combining the variable-region genes and constant-region genes of human IgG, we obtained four independent human monoclonal antibodies specific for tumor necrosis factor-α. This might be a good strategy for generating antigen-specific human monoclonal antibodies using a peptide antigen.

Propionibacterium Acnes Acts as an Adjuvant in in Vitro Immunization of Human Peripheral Blood Mononuclear Cells

We have established an in vitro immunization protocol whereby human peripheral blood mononuclear cells (PBMCs) are initially treated with L-leucyl-L-leucine methyl ester (LLME) and subsequently sensitized with antigen in the presence of interleukin (IL)-2, IL-4, and adjuvant. This protocol resulted in the production of antigen-specific antibodies. PBMCs are potentiated to react with exogenous antigens upon treatment with LLME. We are using this system to investigate the immunomodulatory activity of additives. In the present study, we aimed to evaluate the immunomodulatory activity of Propionibacterium acnes (P. acnes), which is known to exhibit various immunomodulatory effects in murine models, using this in vitro immunization protocol. P. acnes was found to augment the production of antigen-specific antibodies by PBMC, possibly through increased production of inflammatory cytokines and/or increased T-B cell interaction. P. acnes hence appears to act as an adjuvant in the antibody response in in vitro immunization.

Suppression of immunoglobulin production in human peripheral blood mononuclear cells by monocytes via secretion of heavy-chain ferritin.

In vitro antigen stimulation of peripheral blood mononuclear cells (PBMCs) does not induce immunoglobulin (Ig) production. However, pretreatment of PBMCs with l-leucyl-l-leucine methyl ester (LLME) prior to in vitro stimulation removes the suppression of Ig production. In the present study, we attempted to identify the target cells of LLME and determine the mechanisms by which Ig production in PBMCs is suppressed. We found that CD14(+) monocytes are involved in the suppression of Ig production in PBMCs. Furthermore, we confirmed that heavy-chain ferritin derived from CD14(+) monocytes suppresses Ig production in PBMCs, possibly through iron sequestration.

In vitro immunization of Epstein–Barr virus-immortalized B cells augments antigen-specific antibody production

The current method for in vitro immunization (IVI) uses several antigens including toxins, food allergens, pathogenic bacteria, and self-antigen-derived peptides that induce an antigen-specific immune response in peripheral blood mononuclear cells (PBMCs). This protocol, however, requires donor blood collection and preparation of PBMCs before every IVI. In the present study, we aimed to design a more efficient system utilizing B cells immortalized with Epstein–Barr virus (EBV-B) as host cells for IVI to make antigen-specific antibodies. Results showed that previously antigen-sensitized, EBV-B cells exposed to the antigen along with IL-6, CpG oligonucleotides, and CD40 ligand signal produced antigen-specific antibodies. These results provide evidence for a novel and easy method to expand memory-type B cells and produce antigen-specific antibodies.