CD83 Antibody

What is CD83 and what role does it play in immune function?

CD83 is a member of the immunoglobulin superfamily consisting of a single variable-like Ig domain, a transmembrane domain, and a C-terminal cytoplasmic domain. It functions as an important immune checkpoint, originally identified in activated lymphocytes and now recognized as a key marker for activated dendritic cells (DCs) .

Functionally, CD83 contributes to antigen-presenting cell (APC) maturation by binding and sequestering the ubiquitinase ligase MARCH1, which inhibits the enzyme's ability to ubiquitinate and degrade surface MHC class II and CD86 molecules . This mechanism explains how CD83 stabilizes surface expression of these molecules, which are crucial for T cell activation.

Despite being present on activated APCs and causing upregulation of MHC-II and CD86, CD83 signaling appears to promote regulatory functions in various immune cell populations. For DCs, engagement of membrane CD83 (mCD83) reduces their capacity to mature and secrete pro-inflammatory cytokines through the MAPK signaling pathway .

Which cell types express CD83 and how does expression differ between human and mouse models?

CD83 expression is widely distributed among different immune cell types:

While the amino acid sequences of mouse CD83 and human CD83 are 63% identical, the mouse protein lacks a 10-amino acid portion of the extracellular Ig domain, which may influence expression or function . CD83 expression increases on CD4+, CD8+ T, and Treg cells during clinical acute graft-versus-host disease in allogeneic hematopoietic cell transplant recipients .

What types of CD83 antibodies are available for research applications?

Several types of CD83 antibodies have been developed for research and potential therapeutic applications:

• Mouse anti-human CD83 monoclonal antibodies (mAbs): HB15a and HB15e are commonly used for examining CD83 expression in human cells .

• Human anti-human CD83 mAbs: The 3C12C antibody is an affinity-matured human IgG1 Fc-competent monoclonal antibody that has shown potential for therapeutic applications .

• Rat anti-mouse CD83 mAbs: DCR-5 is an example that mimics the properties of human anti-human CD83 therapeutic antibodies .

• Anti-CD83 antibody-drug conjugates (ADCs): CD83 antibodies conjugated with toxins such as monomethyl auristatin E (MMAE) have shown enhanced cytotoxic effects against CD83+ tumor cells .

The choice of antibody depends on the experimental goals, species being studied, and whether detection or functional modulation is desired.

How does CD83 expression change during immune cell activation and maturation?

CD83 expression is dynamically regulated during immune cell activation and maturation. In dendritic cells, CD83 is rapidly upregulated upon maturation stimuli. While immature DCs lack detectable CD83 surface expression, they store CD83 in the Golgi complex and endocytic vesicles, which can be quickly transported to the cell surface upon maturation signals .

For B cells, CD83 expression follows a developmental pattern. Pro-B and early pre-B cells lack expression, whereas late pre-B cells show significant upregulation, with most naïve immature B cells maintaining CD83 expression .

In T cells, CD83 expression is strictly activation-dependent. Both CD4+ and CD8+ T cells, including regulatory T cells, effector memory cells, and central memory cells, only express CD83 upon activation, with stronger expression observed in CD4+ compared to CD8+ T cells .

During clinical acute graft-versus-host disease, CD83 expression increases significantly on CD4+, CD8+ T, and Treg cells, suggesting its role as a potential biomarker for inflammatory conditions .

What methods are optimal for detecting CD83 in different experimental systems?

Several methods can be used to detect CD83 in research settings:

• Flow cytometry: The Michel-19 anti-CD83 clone on FITC or BV711 is commonly used to assess CD83 expression . For optimal results, use specific antibody clones depending on the species and application:

  • For human cells: HB15a, HB15e, and 3C12C antibodies

  • For mouse cells: Michel-19 or DCR-5 antibodies

• Immunohistochemistry: When performing IHC, standard antigen retrieval methods are suitable. For optimal staining of CD83 in tissue sections, consider using biotin-streptavidin amplification systems to enhance sensitivity.

• ELISA for soluble CD83: Enzyme-linked immunosorbent assay can be used to detect soluble CD83 (sCD83) in serum samples . This method has been used to monitor sCD83 levels in Hodgkin lymphoma patients, with levels correlating to clinical response.

• mRNA detection: Several CD83 mRNA isoforms have been described, including those encoding soluble forms. RT-PCR and RNA sequencing can be used to detect these variants across different cell types .

How can researchers distinguish between membrane-bound and soluble forms of CD83?

Distinguishing between membrane-bound CD83 (mCD83) and soluble CD83 (sCD83) is critical for understanding CD83 biology:

• Cell surface staining vs. supernatant analysis: Flow cytometry using non-permeabilizing conditions detects only surface mCD83, while ELISA of culture supernatants or serum samples detects sCD83.

• Western blotting: The molecular weight difference between mCD83 (approximately 43 kDa when fully glycosylated) and sCD83 (approximately 23-25 kDa) allows discrimination by Western blot.

• Molecular approach: PCR with primer sets designed to distinguish between full-length mCD83 and alternatively spliced sCD83 variants can differentiate between expression of the different forms.

The release of sCD83 is predominantly mediated by proteolytic cleavage from membrane-anchored CD83 but may also involve differential splicing to produce a secreted form . High levels of sCD83 have been detected in Hodgkin lymphoma patient sera, which returned to normal in patients who had good clinical responses to chemotherapy .

What are the key considerations when using CD83 antibodies in flow cytometry?

When using CD83 antibodies for flow cytometry, researchers should consider:

• Antibody clone selection: Different clones may recognize distinct epitopes with varying sensitivity. For human samples, HB15a and HB15e are well-characterized mouse anti-human CD83 mAbs with different binding characteristics . For mouse samples, Michel-19 is commonly used .

• Timing of sample collection: Since CD83 expression is dynamic and activation-dependent, especially in T cells and DCs, timing is crucial for capturing the appropriate expression window.

• Panel design: Include markers to identify specific cell populations of interest, as CD83 is expressed by multiple cell types. Lineage-specific markers (CD3, CD19, CD11c, etc.) should be included.

• Controls: Include both positive controls (LPS-stimulated dendritic cells or activated B cells) and negative controls (unstimulated cells or isotype controls).

• Fixation impact: Be aware that some fixation methods may affect CD83 epitope recognition. Test the compatibility of your fixative with your selected CD83 antibody.

• Cytoplasmic versus surface staining: For comprehensive analysis, consider comparing surface staining (non-permeabilized cells) with total CD83 staining (permeabilized cells), as immature DCs store CD83 intracellularly .

How can CD83 antibodies be used to isolate or manipulate specific immune cell populations?

CD83 antibodies can be powerful tools for isolating or manipulating specific immune cell populations:

• Isolation of mature dendritic cells: Anti-CD83 antibodies coupled to magnetic beads can be used to positively select mature DCs from mixed cell populations. This approach yields a highly purified population of DCs for functional studies or therapeutic applications.

• Depletion of activated immune cells: CD83 antibodies can selectively deplete activated APCs capable of stimulating allogeneic T-cells while retaining non-activated APCs that impart tolerance . This strategy has been tested in pre-clinical models using polyclonal rabbit anti-human CD83 antibody and later with the high-affinity human anti-human CD83 IgG1 mAb, 3C12C.

• Induction of regulatory DCs: In mouse models, the rat anti-mouse CD83 mAb DCR-5 has been shown to deplete mature CD83+ conventional DCs (cDCs) and induce regulatory DCs (DCregs), leading to reduced T cell activation and greater Treg induction .

• Modulation of B cell responses: Treatment with anti-CD83 antibodies significantly augmented IgG1 responses to T-cell independent antigens in mice models, underpinned by increased marginal zone B-cell isotype switching .

What controls should be included when using CD83 antibodies in immunoassays?

To ensure reliable results when using CD83 antibodies in immunoassays, include these essential controls:

• Positive controls:

  • Known CD83-expressing cells: LPS-stimulated dendritic cells, activated B cells, or CD83-transfected cell lines.

  • For human samples, Hodgkin lymphoma cell lines (particularly the KM-H2 line) which express high levels of CD83 .

• Negative controls:

  • Isotype-matched control antibodies to control for non-specific binding.

  • CD83-negative cell lines or unstimulated cells known not to express CD83.

  • For specificity testing, CD83-knockout cells or CD83 blocking with recombinant CD83.

• Technical controls:

  • When developing new assays, include titration of antibody concentration to determine optimal signal-to-noise ratio.

  • For ADCs or functional antibodies, include heat-inactivated antibody to control for Fc-independent effects.

• Comparative controls:

  • When working across species, include both human and mouse samples to account for the 63% sequence homology and the missing 10-amino acid portion in mouse CD83 .

  • Compare multiple anti-CD83 clones when possible, as different epitope recognition may yield different results.

What evidence supports targeting CD83 in transplantation and autoimmune disease models?

Targeting CD83 has shown promising results in several disease models:

These findings suggest CD83 is a promising target for therapeutic manipulation in transplantation, inflammation, and autoimmune diseases.

How effective are CD83 antibody-drug conjugates in targeting cancer cells?

CD83 antibody-drug conjugates (ADCs) have shown promising efficacy in targeting CD83-expressing cancer cells:

• Hodgkin Lymphoma (HL):

  • The human anti-human CD83 antibody 3C12C conjugated with monomethyl auristatin E (MMAE) demonstrated enhanced cytotoxicity against CD83+ HL cell lines compared to the unconjugated antibody .

  • While the unconjugated antibody had variable cytotoxic effects when tested on three HL cell lines, toxicity became more pronounced and consistent when conjugated to MMAE .

• Mantle Cell Lymphoma (MCL):

  • CD83 is expressed on MCL cell lines and patient samples, making it a potential target for therapy in this currently incurable non-Hodgkin lymphoma .

  • CD83 ADC effectively killed CD83+ MCL in vitro and in a xenogeneic mouse model .

  • Interestingly, even though CD83 expression in Mino cells (an MCL cell line) is not as high as in classical Hodgkin lymphoma cells (KM-H2), they showed similar sensitivity to the anti-CD83 ADC, possibly due to hypersensitivity to the MMAE toxin or faster internalization of the antibody .

• Bystander effect:

  • ADCs have shown to be effective not only against target antigen-positive cells but also neighboring antigen-negative cells, dependent on the nature of the reducible disulfide bond linker and the release of the payload .

  • This bystander effect may enhance the efficacy of CD83 ADCs in heterogeneous tumors.

ADCs have shown to be more effective than naked antibodies over a wider range of antigen expression levels, making them particularly attractive for targeting CD83, which may have variable expression levels on cancer cells .

What are the mechanisms by which anti-CD83 antibodies modulate immune responses?

Anti-CD83 antibodies modulate immune responses through several mechanisms:

• Depletion of CD83+ cells:

  • Both mouse anti-human CD83 mAbs and human anti-human CD83 mAb (3C12C) mediate antibody-dependent cell cytotoxicity (ADCC) against CD83+ cells, particularly activated DCs .

  • Treatment with 3C12C in non-human primates resulted in specific reductions in CD83+ populations including CD1c+ DCs and B cells, without affecting total blood cell counts .

• Modulation of antigen presentation:

  • By depleting mature DCs, anti-CD83 antibodies reduce the capacity for alloreactive T cell presentation and proliferation .

  • This selectively prevents allogeneic T-cell stimulation while preserving memory T-cell reactivity to viral and tumor antigens .

• Induction of regulatory DCs:

  • The rat anti-mouse CD83 mAb DCR-5 not only depletes mature CD83+ conventional DCs but also induces regulatory DCs, leading to reduced T cell activation and greater Treg induction .

• Neutralization of soluble CD83:

  • High levels of soluble CD83 (sCD83) have been detected in Hodgkin lymphoma patient sera, and this sCD83 inhibits T-cell proliferation .

  • Anti-CD83 antibodies can partially reverse this inhibitory effect by neutralizing sCD83 .

• B cell modulation:

  • Treatment with anti-CD83 antibodies induces a dramatic increase in antigen-specific IgG responses to immunization in mice, demonstrating CD83's regulatory role in B cell function .

  • Targeting CD83+ B cells with anti-CD83 mAb in a human PBMC xenograft model inhibited B-cell responses to specific antigens without causing pan B-cell depletion .

These mechanisms highlight the complex immunomodulatory effects of anti-CD83 antibodies, which can be exploited for therapeutic purposes in various disease contexts.

How do soluble and membrane-bound CD83 differentially affect immune responses?

Soluble CD83 (sCD83) and membrane-bound CD83 (mCD83) have distinct immunological functions:

Soluble CD83 (sCD83):

• sCD83 is detectable at low concentrations in the serum of healthy individuals and at elevated levels in certain disease states like Hodgkin lymphoma .

• Multiple studies have revealed immunosuppressive functions of sCD83 .

• sCD83 inhibits T-cell proliferation, and anti-CD83 antibody can partially reverse this inhibitory effect .

• Human DCs secrete considerable amounts of sCD83 when exposed to different commensal bacteria strains, suggesting a role in regulating intestinal homeostasis .

• For binding to activated human primary T cells, the formation of dodecameric sCD83 multimers appears to be a prerequisite, which is absent when using conventional dimerized sCD83 molecule .

Membrane-bound CD83 (mCD83):

• mCD83 on DCs contributes to cell maturation by increasing surface expression of MHC-II and CD86 through interaction with the E3-ubiquitin-ligases of the MARCH family .

• Engagement of mCD83 with antibody or homotypic binding with CD83-expressing cell lines reduces DC capacity to mature and secrete pro-inflammatory cytokines via the MAPK signaling pathway .

• mCD83 expression by mouse B or T-cells increases their longevity in vivo .

• Transgenic overexpression of mCD83 in mouse B-cells results in inhibitory function, including decreased capacity to proliferate, class-switch, and secrete immunoglobulins, despite increased surface MHC-II and CD86 levels .

Understanding these differential effects is crucial for developing targeted therapeutic strategies that specifically modulate either mCD83 or sCD83 functions.

What challenges exist in translating CD83-targeted therapies to clinical applications?

Several challenges must be addressed before CD83-targeted therapies can be successfully translated to clinical applications:

What are the emerging applications of CD83 antibodies in immunotherapy research?

CD83 antibodies are showing promise in several emerging immunotherapeutic applications:

• Combination therapy for lymphomas:

  • CD83 ADC in combination with chemotherapy has potential to enhance efficacy of treatment for mantle cell lymphoma, which is currently incurable .

  • The study by Li et al. demonstrated that CD83 is a new potential biomarker and therapeutic target for Hodgkin lymphoma, with antibody-toxin conjugates showing specific killing of CD83+ Hodgkin lymphoma cells .

• Biomarker for disease activity and treatment response:

  • Serum levels of sCD83 measured by ELISA correlated with clinical response in Hodgkin lymphoma patients, suggesting its potential as a biomarker for treatment monitoring .

  • Increased CD83 expression on CD4+, CD8+ T, and Treg cells is associated with clinical acute graft-versus-host disease in allogeneic hematopoietic cell transplant recipients, potentially serving as a diagnostic marker .

• Modulation of intestinal immunity:

  • Given that CD83 plays a crucial role in regulating intestinal homeostasis and anti-bacterial immunity, CD83 antibodies might have applications in treating inflammatory bowel diseases .

  • Conditional knockout of CD83 in DCs resulted in enhanced Th1 and Th17 T cell responses, while B cell-specific depletion of CD83 had different effects on immune responses to pathogens .

• Engineering improved CD83 antibodies:

  • Development of bispecific antibodies targeting CD83 alongside other immune checkpoint molecules could enhance therapeutic efficacy.

  • Engineering antibodies that specifically neutralize sCD83 while sparing mCD83 (or vice versa) could allow for more precise immunomodulation.

• Vaccination strategies:

  • Understanding how CD83 regulates B cell responses could inform the development of vaccines that induce optimal antibody responses.

  • Treatment with anti-CD83 mAb was found to induce a dramatic increase in antigen-specific IgG responses to immunization in mice , suggesting potential applications in vaccine adjuvant development.

These emerging applications highlight the versatility of CD83 antibodies as tools for immunomodulation in various disease contexts.