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Pan-isotype + Subclass Profiling
Decode the Human Immune System
with True Pan-isotype and Subclass-level Detail
Analyze pan-isotypes, including all subclasses with
HuProt™ and VirScan® PhIP-Seq for massively-multiplexed insights
Why Isotype and Subclass Differentiation Matters in Autoantibody Research
Serum autoantibody studies have traditionally relied on pan-IgG analysis, which detects IgG1, IgG2, IgG3, and IgG4 simultaneously, but without differentiation. While this method provides valuable insights, it captures only a portion of the humoral immune response encoded in a serum sample. Each IgG subclass has unique structural features that affect its function, and differences in subclass abundance can offer important clues about disease risk, diagnosis, or prognosis. This functional and structural diversity extends across all antibody isotypes and subclasses, highlighting the importance of detailed analysis for more comprehensive immune profiling.
The ability to detect any antibody isotype or subclass marks an exciting new chapter in autoantibody research - bringing a more complete view of the immune response within reach. Just as studying the full spectrum of T cells is vital to understanding cell-mediated immunity, appreciating the diversity among antibody isotypes and subclasses is key to fully understanding humoral immunity. While technological limitations previously restricted this level of detail, CDI Labs’ new pan-isotype and subclass analysis capabilities now make it possible to explore these differences with unprecedented depth.
Antibodies Are Made Up of 9 Different Isotypes and Subclasses
Antibodies are immune system proteins that recognize and neutralize harmful pathogens. They are classified into different isotypes based on their heavy chain constant regions. Human B cells produce five antibody isotypes: IgG (with four subclasses), IgD, IgE, IgA (with two subclasses and can form dimers), and IgM (which can form pentamers). Each isotype has distinct functions, locations, and timing during the immune response.
IgA
Mucosal IgA1 and IgA2 are critical to sculpting the microbiome and fighting pathogens in the gut and lungs
IgM
Pentameric IgM is the first to arise to new exposures
IgE
IgE is known for its role in allergic responses, but is also able to kill tumors and create neurologic inflammatory disease
IgG
IgG1 is the most abundant antibody of all and is a great all-around performer with complement fixing, cross-linking, and cytotoxic effects
IgG2 has a less flexible hinge, is the dominant anti-carbohydrate antibody, believed critical in the defense against bacterial cell walls
IgG3 has the most flexible hinge, giving better access to Fc receptors and complement fixing; it is often seen as the most cytotoxic IgG
IgG4 is barely able to fix complement and unable to cross-link due to its unique property of Fab-arm exchange: most IgG4 molecules in circulation are actually bispecifics of two separate origins
IgD
While IgD is often referenced as mere ‘soluble B cell receptor’, it has also been linked to direct biologic functions
The Clinical Relevance of Antibody Isotypes and Subclasses in Disease and Therapy
Antibody subclass matters for patient outcomes. Lung adenocarcinoma patients with unfavorable IgG4-to-total-IgG ratios have poor survival,1 while tumor-infiltrating B cells with different isotype profiles correlate directly with protective immune responses.2 Patients lacking specific isotypes like IgA, IgG3, or IgG4 can suffer chronic respiratory infections.3 Clinical evidence for isotype-specific analysis is overwhelming and spans virtually every area of human health. Entire disease classifications now revolve around specific antibody subclasses, with IgG4-associated diseases4 representing a distinct pathological category that would be invisible to traditional pan-IgG analysis.
The Value of Multi-isotype Data in...
- Autoimmune Disease -
Systemic Lupus Erythematosus (SLE)
High levels of IgG1 anti-dsDNA are associated with the development and severity of lupus nephritis
IgE autoantibodies have been associated with specific clinical manifestations like nephritis or skin involvement, or with more severe disease
Rheumatoid Arthritis (RA)
IgG anti-citrullinated protein antibodies (IgG-ACPA) are the most specific marker for RA
IgA-ACPA can increase diagnostic sensitivity, especially in seronegative patients, and may have prognostic implications
Chronic Inflammatory Demyelinating Polyneuropathy (CIDP)
In a subset of CIDP patients, the predominant subclass is IgG4
IgG4 autoantibodies are thought to disrupt the paranodal structures on nerve fibers, leading to demyelination and impaired nerve conduction
- Neurodegenerative Disease -
Alzheimer’s Disease
IgM Anti-Aβ/Tau studies suggest that naturally occurring IgM autoantibodies against Aβ and Tau aggregates may play a protective role; they are believed to facilitate the removal of toxic protein aggregates from the brain or inhibit their aggregation
Amyotrophic Lateral Sclerosis (ALS) and Motor Neuron Disease Mimics
High titers of IgM anti-GM1 autoantibodies are a hallmark of Multifocal Motor Neuropathy (MMN), a treatable immune-mediated peripheral neuropathy that can mimic ALS
Anti-NMDA Receptor Encephalitis (IgG1 vs. other IgG subclasses)
Diagnosis relies on detecting IgG autoantibodies against the NMDAR - specifically, the pathogenic antibodies are almost exclusively IgG1; this subclass has the ability to cause receptor internalization (leading to symptoms)
- Cancer -
Cancer
IgM autoantibodies are often the first antibodies produced in response to newly emerging tumor-associated antigens; This makes them highly promising biomarkers for early cancer detection
Immunotherapy
Patients with pre-existing autoantibodies, especially IgG1 autoantibodies against self-antigens, may be at a higher risk of developing irAEs (immune-related adverse events)
Effective Anti-tumor Response
A robust response dominated by IgG1 and/or IgG3 autoantibodies against specific TAAs might indicate a more effective host anti-tumor immune response
In some cancers, the presence or higher levels of IgG1 and/or IgG3 autoantibodies against certain TAAs can correlate with a better prognosis or improved survival
Enabling True Pan-isotype + Subclass Profiling
CDI Labs delivers comprehensive pan-isotype analysis across all major human antibody classes (pan-IgA, IgA1, IgA2, IgD, IgE, pan-IgG, IgG1, IgG2, IgG3, IgG4, IgM) through our established HuProt™ and VirScan® platforms. Whether analyzing 21,000+ proteins on HuProt microarrays or conducting viral serology via VirScan's isotype-specific pulldowns, researchers can now target specific subclasses of interest or pursue complete pan-isotype profiling.
Using HuProt, you can now design discovery studies to reveal both autoantibody protein targets and their precise isotype and subclass. Multi-isotype/subclass validation studies can then be conducted on a larger scale using HuProt Focused Microarrays. Alternatively, you can take pan-IgG data (from current or past studies) and enrich it with pan-isotype/subclass data for a specific set of proteins during the validation phase, again using HuProt Focused Microarrays.
CDI Labs' Highly-specific Isotypes and Subclasses
The above chart shows final HuProt microarray validation Z-Score hits for final clones versus critical validation antigens stained with anti-mouse secondary antibody. All hits are >4-fold increased versus secondary-only and a Z-Score >3 on log2 transformed data across that entire array. Non-hits are set to 0.
- Isaeva, O. I. et al. Intratumoral immunoglobulin isotypes predict survival in lung adenocarcinoma subtypes. J. Immunother. Cancer 7, 279 (2019).
- Harris, R. J. et al. Tumor-Infiltrating B Lymphocyte Profiling Identifies IgG-Biased, Clonally Expanded Prognostic Phenotypes in Triple-Negative Breast Cancer. Cancer Res. 81, 4290–4304 (2021).
- Ozkan, H., Atlihan, F., Genel, F., Targan, S. & Gunvar, T. IgA and/or IgG subclass deficiency in children with recurrent respiratory infections and its relationship with chronic pulmonary damage. J Investig Allergol Clin Immunol 15, 69–74 (2005).
- Rispens, T. & Huijbers, M. G. The unique properties of IgG4 and its roles in health and disease. Nat. Rev. Immunol. 23, 763–778 (2023)
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