IL 7 Antibody

What are IL-7/anti-IL-7 mAb complexes and why are they important?

IL-7/anti-IL-7 mAb complexes are prebound combinations of IL-7 cytokine with anti-IL-7 neutralizing monoclonal antibodies (typically clone M25 in mouse studies). Despite using a neutralizing antibody, these complexes dramatically increase the biological activity of IL-7 in vivo by 50-100 fold compared to free IL-7 . These complexes induce massive expansion of pre-B cells, increase thymopoiesis in normal mice, restore thymopoiesis in IL-7-deficient mice, and induce marked homeostatic proliferation of both naive and memory CD4+ and CD8+ cell subsets even under normal T cell-replete conditions .

How does IL-7 receptor expression change during treatment with IL-7?

During IL-7 treatment, both IL-7Rα surface expression and mRNA levels decrease significantly. This downregulation occurs during the treatment period and returns to baseline after the end of treatment . This receptor downregulation may explain why maximum therapeutic effects of IL-7 are often reached early in treatment courses, as demonstrated in patients who received only the first three doses of recombinant human IL-7 (rhIL-7) but showed similar cell cycling patterns and absolute lymphocyte count increases as those receiving complete treatment courses .

What mechanisms explain the enhanced potency of IL-7/anti-IL-7 mAb complexes?

The enhanced potency of IL-7/anti-IL-7 mAb complexes is explained by two key mechanisms:

• Fc domain contribution: By engaging the neonatal Fc receptor, the Fc domain extends the in vivo lifespan of IL-7/M25 complexes and accounts for the majority of their activity .

• Fab domain contribution: The IL-7-neutralizing Fab domain provides an additional, albeit smaller, contribution, possibly by serving as a cytokine depot .

IL-7/antibody complexes are potent because they prolong IL-7 availability in vivo by decreasing both specific and nonspecific consumption . This is particularly important because IL-7 has a massive calculated volume of distribution, implying that an IL-7 sink exists in vivo which can rapidly absorb exogenous cytokine .

How does intermittent versus continuous IL-7 signaling affect T cell homeostasis?

Naive CD8 T cells require IL-7 signaling to be intermittent, not continuous . The contrast between these signaling patterns is profound:

Continuous IL-7 signaling prolongs expression of phosphorylated STAT5, which activates IFN-γ gene expression and ultimately triggers cytokine-induced cell death (CICD) .

What is cytokine-induced cell death (CICD) in the context of IL-7 signaling?

Cytokine-induced cell death (CICD) is a form of T cell death resulting from continuous IL-7 signaling . Key characteristics include:

• It occurs when naive CD8 T cells receive continuous rather than intermittent IL-7 signals

• Continuous IL-7 signaling results in >90% of cells becoming apoptotic after 14 days

• The mechanism involves upregulation of pro-apoptotic proteins including active caspase-3

• CICD is mediated by IFN-γ: continuous IL-7 signaling induces IFN-γ expression, which triggers cell death

• Blocking IFN-γ or using IFN-γ-deficient T cells prevents CICD and results in continuous exponential growth under IL-7 stimulation

• Adding exogenous IFN-γ to IFN-γ-deficient CD8 T cells restores the CICD effect

What role does IFN-γ play in IL-7 antibody-mediated effects?

IFN-γ plays a critical role in mediating the effects of continuous IL-7 signaling:

• Continuous IL-7 signaling activates STAT5, which binds to and activates the IFN-γ gene

• The resulting IFN-γ production acts as a negative feedback mechanism, triggering CICD

• When IFN-γ signaling is blocked (via antibodies or genetic deficiency), continuous IL-7 signaling leads to exponential T cell growth

• This exponential growth can be halted by adding exogenous IFN-γ

These findings demonstrate that IFN-γ is a critical mediator of the negative effects of continuous IL-7 signaling and that manipulating IFN-γ signaling could be a strategy to enhance IL-7 antibody therapies.

How do IL-7 antibodies affect different T-cell subpopulations?

IL-7 antibodies affect T-cell subpopulations differently based on their IL-7 receptor expression levels and intrinsic properties:

The differential expansion leads to a decreased proportion of regulatory T cells relative to other T cell populations, which may have important implications for autoimmunity and anti-tumor responses .

What effects do IL-7 antibodies have on T-cell repertoire diversity?

IL-7 treatment, particularly recombinant human IL-7 (rhIL-7), significantly broadens T-cell repertoire diversity in both CD4+ and CD8+ T cells . Within 3 weeks of treatment initiation, rhIL-7 results in a marked expansion of T cells which remain functional (with conserved or increased in vitro responsiveness to anti-CD3 stimulation) and exhibit a rejuvenated profile resembling that seen early in life . This broadening of T-cell repertoire may be beneficial for immune reconstitution in lymphodepleted individuals or for enhancing responses to vaccination.

What immunogenicity concerns exist for IL-7 receptor antibodies in clinical applications?

Significant immunogenicity has been observed with some IL-7 receptor antibodies:

• In a phase I study of anti-IL-7 receptor monoclonal antibody GSK2618960, anti-drug antibodies (ADAs) developed in 83% and 100% of treated subjects in the 0.6 and 2.0 mg/kg dose cohorts, respectively

• 64% of ADA-positive subjects had detectable neutralizing activity

• GSK2618960-specific memory B cells were detected, indicating development of immunological memory against the drug

• Ex vivo stimulation showed strong CD4+ T cell proliferation responses to GSK2618960

• The antibody was found to bind to monocyte-derived dendritic cells and increase expression of activation markers CD83, CD86, and CD209

These findings suggest that receptor-mediated activity by the antibody likely contributed to its high immunogenicity, presenting a significant challenge for clinical development.

What are the potential clinical applications of IL-7 antibody treatments?

Based on the search results, IL-7 antibody treatments have several potential clinical applications:

• Immune reconstitution: rhIL-7 induces marked expansion of T cells with a rejuvenated profile, making it useful for reconstituting lymphodepleted individuals

• Cancer immunotherapy: The strong stimulatory activity of IL-7/mAb complexes could enhance anti-tumor immune responses

• Vaccination adjuvant: IL-7/mAb complexes enhance the magnitude of primary responses of antigen-specific naive CD8+ cells

• Autoimmune disease treatment: Anti-IL-7 receptor antibodies could potentially treat autoimmune conditions where IL-7 signaling is implicated

The search results specifically mention that rhIL-7 "induces an age-independent marked expansion of the T-cell mass resulting in a rejuvenated T-cell profile with an increased T-cell repertoire diversity and a decreased proportion of regulatory T cells" .

What techniques are recommended for measuring IL-7 signaling in T-cells?

Several techniques can be used to measure IL-7 signaling in T-cells:

What controls should be included in IL-7 antibody experiments?

Based on the search results, appropriate controls for IL-7 antibody experiments should include:

• Free IL-7 without antibody complex: To demonstrate the enhanced potency of IL-7/mAb complexes

• Isotype control antibodies: Such as anti-β amyloid antibody or anti-RSV antibody

• IFN-γ blocking conditions: When studying continuous IL-7 signaling, to distinguish direct IL-7 effects from those mediated by IFN-γ

• IFN-γ or IFN-γR deficient cells: As additional controls to confirm the role of IFN-γ in observed effects

• Different doses of IL-7 antibodies: To establish dose-response relationships

• Time-course assessments: To capture the kinetics of responses, as effects may vary significantly over time

How can researchers distinguish between direct and indirect effects of IL-7 antibodies?

Researchers can distinguish between direct and indirect effects through several approaches:

• Genetic knockout models:

  • Using IFN-γ or IFN-γR deficient cells to identify effects mediated by IFN-γ

  • IL-7 receptor transgenic models to study continuous IL-7 signaling

• Blocking experiments:

  • Anti-IFN-γ antibodies to block IFN-γ-mediated effects

  • Adding exogenous recombinant IFN-γ to confirm its role

• Time-course studies:

  • Examining early vs. late effects to distinguish primary from secondary effects

  • Monitoring how long different effects persist after treatment cessation

• Cell subset analysis:

  • Comparing effects on different T-cell subpopulations with varying levels of IL-7R expression

  • For example, comparing effects on regulatory T cells (which have low IL-7Rα expression) vs. other CD4+ T cells