IL 21 Mouse

What is IL-21 and what are its primary cellular sources in mice?

IL-21 is a type I cytokine that plays crucial roles in regulating immune responses in mice. The primary cellular sources of IL-21 are activated CD4+ T cells, particularly T follicular helper (TFH) cells. In mouse models of hepatitis B virus (HBV) infection, TFH cells in the liver produce IL-21 in an HBV-dependent manner . Research demonstrates that IL-21 production is age-dependent, with adult mice showing higher HBV-dependent IL-21 production in the liver compared to young mice .

Which cell types express the IL-21 receptor in the murine immune system?

The IL-21 receptor (IL-21R) is expressed on multiple immune cell populations in mice, including T cells, B cells, and natural killer (NK) cells . The receptor is most closely related to the IL-2R β-chain and, like several other cytokine receptors, utilizes the common cytokine receptor γ-chain (γc) for signaling . IL-21R signaling involves the activation of Jak1 and Jak3 as well as Stat1, Stat3, and Stat5 transcription factors .

How does IL-21 affect B cell development and function in mice?

IL-21 has complex and context-dependent effects on B cell development and function:

• It regulates IgG1 production and cooperates with IL-4 for the production of multiple antibody classes in vivo

• IL-21 induces death of resting B cells but promotes differentiation of B cells into postswitch and plasma cells

• This dual capacity explains how IL-21 can be proapoptotic for B cells in vitro yet critical for antigen-specific immunoglobulin production in vivo

• IL-21 induces expression of both Blimp-1 and Bcl-6, key transcription factors that regulate B cell maturation and terminal differentiation

• IL-21R−/− mice have markedly diminished IgG1 but greatly elevated IgE levels in response to antigen

How does age affect IL-21 production and immune responses in mouse models of hepatitis B?

Research using mouse models of HBV infection demonstrates significant age-dependent differences in IL-21 production and subsequent immune responses:

• Adult mice show higher HBV-dependent IL-21 production in the liver compared to young mice

• Young mice exhibit several IL-21-related immune deficits including:

  • Inability to generate HBsAb responses

  • Fewer CD8+ T cells in the liver

  • Inability to diversify and sustain strong HBV-specific T cell responses

  • Paucity of IL-21-producing TFH cells in the liver

  • Fewer IgG-expressing B cells in the liver

These findings parallel human HBV infection patterns, where neonates and children usually develop chronic infection while adults typically clear the virus. The research suggests that decreased IL-21 production in younger subjects may hinder generation of crucial CD8+ T and B cell responses necessary for viral clearance .

What is the pathogenic role of IL-21 in autoimmune disease mouse models?

IL-21 appears to play significant pathogenic roles in multiple autoimmune disease mouse models:

• In the MRL-Fas(lpr) lupus-prone mouse model:

  • Blocking IL-21 with IL-21R.Fc fusion protein reduced disease symptoms including proteinuria, IgG glomerular deposits, and circulating dsDNA autoantibodies

  • Treatment with IL-21R.Fc resulted in reduced splenic T lymphocytes and altered B lymphocyte function

• BXSB-Yaa mice, which develop a systemic lupus erythematosus-like disease, have greatly elevated IL-21 levels

• From a clinical perspective, blocking IL-21 in SLE patients may represent a promising therapeutic approach based on mouse model findings

How do IL-21-deficient mouse models differ from IL-21R-deficient models in experimental outcomes?

Different experimental approaches to disrupting IL-21 signaling can yield varying outcomes:

• IL-21−/− mice show decreased γδT17 cells in the spleen and lymph nodes

• IL-21R−/− mice demonstrate:

  • Decreased Vγ4+ γδT17 cells in the spleen and lung

  • Increased γδT17 cells in the lung and peritoneal cavity according to some studies

  • Markedly diminished IgG1 but elevated IgE levels in response to antigen

These differences highlight the complexity of IL-21 signaling and suggest possible compensatory mechanisms or differential effects on specific cell populations depending on whether the ligand or receptor is targeted.

How do researchers reconcile contradictory findings regarding IL-21's effect on different γδT17 cell subsets?

The literature reveals apparently contradictory findings regarding IL-21's effects on γδT17 cells:

These seemingly contradictory findings may be reconciled by considering the tissue-specific distribution of γδT17 cell subsets:

• Vγ4+ γδT17 cells predominate in the spleen

• Vγ6+ γδT17 cells are dominant in the lung and peritoneal cavity

Thus, IL-21 appears required for peripheral maintenance of Vγ4+ γδT17 cells but may have different effects on Vγ6+ γδT17 cells. Environmental factors and commensal bacteria may also influence these tissue-specific differences .

What mouse models are available for studying IL-21 function?

Several mouse models are available for investigating IL-21 biology:

• Genetic models:

  • IL-21 knockout mice (IL-21−/−)

  • IL-21 receptor knockout mice (IL-21R−/−)

  • IL-21 transgenic mice with overexpression of IL-21

• NSG mice (NOD.Cg-Prkdcscid Il2rgtm1Wjl/SzJ) which lack T cells, B cells, NK cells and have deficient signaling for 6 cytokines including IL-21

• Disease models:

  • MRL-Fas(lpr) lupus-prone mice (useful for studying IL-21 in autoimmunity)

  • BXSB-Yaa mice which develop lupus-like disease with elevated IL-21

• Experimental models:

  • Mixed bone marrow chimera (mBMC) models to study cell-intrinsic effects of IL-21 signaling

  • HBVEnvRag mice receiving adoptively transferred splenocytes

What approaches can be used to modulate IL-21 signaling in experimental mouse models?

Researchers can manipulate IL-21 signaling through various approaches:

• Genetic approaches:

  • Using IL-21 or IL-21R knockout mice

  • Transgenic overexpression of IL-21

• Protein-based approaches:

  • IL-21R.Fc fusion protein (acts as a decoy receptor to block IL-21)

  • Treatment with IL-21R.Fc has been shown to reduce symptoms in lupus models

• Transfer approaches:

  • Adoptive transfer experiments

  • Mixed bone marrow chimeras (mBMC)

How should researchers analyze the role of IL-21 in innate versus adaptive immunity?

IL-21 appears to function at the interface between innate and adaptive immunity:

• IL-21 limits NK cell responses while promoting antigen-specific T cell activation

• IL-21 may serve as a mediator of the transition from innate to adaptive immunity

• IL-21 contributes to effective anti-viral responses through:

  • Enhancing CD8+ T cell responses

  • Supporting B cell differentiation and antibody production

  • Influencing γδT17 cells which bridge innate and adaptive immunity

When analyzing this role, researchers should:

• Study both early (innate) and late (adaptive) timepoints in infection models

• Examine IL-21's effects on both innate cells (NK, γδT) and adaptive cells (αβT, B cells)

• Use both in vitro systems and in vivo models to capture the full spectrum of IL-21 functions

How can researchers effectively study age-dependent effects of IL-21?

When investigating age-dependent effects of IL-21, researchers should consider:

• Including multiple age groups in experimental design (young vs. adult mice)

• Analyzing IL-21 production capacity at different ages

• Using adoptive transfer experiments between different age groups

• Correlating findings in mouse models with human samples (as done in HBV studies comparing acute adult infection with chronic infection)

• Examining age-specific differences in IL-21R expression and downstream signaling

• Considering environmental factors that may change with age

How does IL-21 contribute to experimental autoimmune encephalomyelitis (EAE) pathogenesis?

Recent research has revealed that:

• IL-21 signaling in γδT17 cells exacerbates experimental autoimmune encephalomyelitis (EAE)

• IL-21 is required for the peripheral maintenance of Vγ4+ γδT17 cells but is dispensable for their thymic development

• The role of IL-21 in EAE appears to be complex and may involve both direct effects on pathogenic cell populations and indirect effects on regulatory mechanisms

How does IL-21 interact with other cytokines in mouse immune responses?

IL-21 functions within a complex network of cytokines:

• IL-21 cooperates with IL-4 for the production of multiple antibody classes in vivo

• IL-21R utilizes the common cytokine receptor γ-chain (γc) shared with IL-2, IL-4, IL-7, IL-9, and IL-15

• NSG mice lack signaling for 6 cytokines including IL-2, IL-4, IL-7, IL-9, IL-15, and IL-21

• Understanding the hierarchical and synergistic relationships between these cytokines requires careful experimental design with appropriate controls

What are the contradictory findings in IL-21 research that require further investigation?

Several areas of IL-21 biology show apparently contradictory results that merit further study:

• Effects on γδT17 cells: decreased in spleen/LNs but increased in lung/peritoneal cavity in some studies

• B cell effects: pro-apoptotic for resting B cells but promotes differentiation in activated B cells

• Tissue-specific effects: different outcomes in different anatomical locations

• Age-dependent effects: different roles in young versus adult immune responses

These contradictions highlight the context-dependent nature of IL-21 function and suggest the need for more nuanced experimental approaches.

What are optimal methods for detecting and measuring IL-21 in mouse tissues?

Researchers studying IL-21 should consider multiple detection methods:

• Gene expression:

  • qPCR for IL-21 mRNA expression as used in human PBMC studies

  • RNA isolation from specific tissues or sorted cell populations

• Protein detection:

  • Flow cytometry for intracellular IL-21 in specific cell populations

  • Immunohistochemistry for tissue localization

  • ELISA for secreted IL-21

• Functional assays:

  • B cell differentiation and antibody production as readouts of IL-21 activity

  • T cell activation and proliferation assays

  • Reporter systems for IL-21 signaling

What control models are essential for IL-21 research?

When designing IL-21 studies, researchers should include appropriate controls:

• Genetic controls:

  • Wild-type littermates for IL-21−/− or IL-21R−/− mice

  • Isotype controls for blocking antibodies or fusion proteins

• Age-matched controls for age-dependent studies

• Mixed bone marrow chimeras to distinguish cell-intrinsic from cell-extrinsic effects

• Disease model controls:

  • Non-autoimmune strains when studying autoimmune models

  • Uninfected controls when studying infection models