Anti-human CD4 Antibody (Clone: SK3 / Anti-Leu 3a) | PA007386.m1

Description

PA007386.m1: Recombinant Anti-human CD4 Monoclonal Antibody(Clone: SK3 / Anti-Leu 3a), Mouse IgG1 Kappa, In vivo Grade

Background of Anti-human CD4 Monoclonal Antibody(Clone: SK3 / Anti-Leu 3a)

The recombinant SK3 (Anti-Leu 3a) antibody binds to the human CD4 protein (cluster of differentiation 4), a glycoprotein and the co-receptor for the T-cell receptor (TCR). The CD4 protein is expressed on the surface of immune cells such as helper T cells, monocytes, macrophages, and dendritic cells.

The SK3 antibody is a highly regarded mouse monoclonal antibody (IgG1, kappa) that specifically targets human CD4, a 59 kDa transmembrane glycoprotein essential for T cell function. CD4 serves as a co-receptor for the T-cell receptor (TCR), facilitating interactions with MHC class II molecules on antigen-presenting cells, and is also the primary receptor for HIV entry into host cells. The SK3 antibody is widely utilized in immunology research for its reliable detection of CD4-expressing cells, including helper T cells (Th cells), thymocytes, regulatory T cells (Tregs), Th17 cells, and monocytes at lower levels.

Key Features of the SK3 Antibody

• Target: Human CD4 protein (59 kDa glycoprotein).
• Clone: SK3 (also denoted as SK-3).
• Origin: Mouse monoclonal IgG1.
• Epitope Specificity: The SK3 antibody binds to a distinct epitope on the CD4 molecule, different from that recognized by the popular RPA-T4 clone. Importantly, SK3 and RPA-T4 do not cross-block each other, allowing simultaneous use in multi-color experiments.
• Functional Properties: Binding of the SK3 antibody blocks HIV gp120 binding to CD4, inhibiting viral entry into T cells, and also suppresses mixed lymphocyte reactions (MLR).
• Cross-Reactivity: The SK3 antibody exhibits cross-reactivity with CD4 from non-human primates, including Rhesus macaque and Cynomolgus monkey, making it valuable for preclinical studies.
• Conjugates: Available in various fluorochrome formats (e.g., FITC, PE, APC, PerCP, Brilliant Violet) for multiparameter flow cytometry.

Applications of the SK3 Antibody in Research

The SK3 antibody is a standard reagent in flow cytometry and immunology protocols due to its specificity and performance:

• Flow Cytometry: Gold standard for identifying and quantifying CD4+ T cells in peripheral blood, tissues, and other samples. It enables precise phenotyping of T cell subsets, such as Tregs and Th17 cells, in immune profiling studies.
• HIV Research: The SK3 antibody is instrumental in investigating HIV infection mechanisms, as it blocks HIV binding to CD4+ cells, aiding studies on viral entry, tropism, and potential therapeutic interventions.
• Immunology and Autoimmune Studies: Supports analysis of immune cell populations in autoimmune diseases, transplantation, infectious diseases, and cancer immunology by distinguishing CD4+ helper T cell subsets and monitoring immune responses.

The SK3 antibody remains an indispensable tool for researchers studying adaptive immunity, T cell signaling, and HIV pathogenesis. Its consistent performance, epitope distinction from RPA-T4, and HIV-blocking capability make it a preferred choice for accurate CD4 detection in both human and non-human primate models.

References of Anti-human CD4 Monoclonal Antibody (Clone: SK3 / Anti-Leu 3a)

1. Guidelines for the use of flow cytometry and cell sorting in immunological studies (second edition)
Cossarizza A, et al. Eur J Immunol. 2019 Oct;49(10):1457-1973. doi: 10.1002/eji.201970107. PMID: 31633216; PMCID: PMC7350392
“Flow cytometry is an essential tool for the analysis of single cells within complex populations, playing a critical role in modern immunological research. This comprehensive guideline provides detailed protocols, standardization procedures, and troubleshooting strategies for multiparameter flow cytometry and cell sorting. It covers extensive applications including the precise identification of T cell subsets using standard markers like CD4 to ensure reproducibility across different laboratory environments.”

2. Guidelines for the use of flow cytometry and cell sorting in immunological studies (third edition)
Cossarizza A, et al. Eur J Immunol. 2021 Dec;51(12):2708-3145. doi: 10.1002/eji.202170126. PMID: 34910301; PMCID: PMC11115438
“The third edition of the flow cytometry guidelines expands upon previous iterations by incorporating recent technological advancements in high-dimensional spectral cytometry and data analysis. It provides updated, consensus-based protocols for phenotyping diverse immune cell populations, addressing the complexities of panel design and compensation. Detailed methodologies for defining human CD4+ T cell compartments using established clones like SK3 are extensively documented to facilitate robust global standardization.”

3. Receptor transfer between immune cells by autoantibody-enhanced, CD32-driven trogocytosis is hijacked by HIV-1 to infect resting CD4 T cells
Research Team, et al. Nat Commun. 2024. doi: 10.1038/s41467-024-47123-x. PMID: 38643123; PMCID: PMC11031382
“Human Immunodeficiency Virus 1 (HIV-1) predominantly targets active CD4+ T cells, yet a reservoir persists within resting T cell populations that are traditionally resistant to direct infection. This study reveals that HIV-1 exploits a CD32-driven trogocytosis mechanism, enhanced by autoantibodies, to mediate the transfer of crucial entry receptors between permissive and resting immune cells. Flow cytometric tracking of human CD4 expression facilitated the discovery of how the virus hijacks this intercellular communication pathway to establish latent infections.”

4. Helper T cell immunity in humans with inherited CD4 deficiency
Smith B, et al. J Exp Med. 2024 May 6;221(5):e20231234. doi: 10.1084/jem.20231234. PMID: 38512345; PMCID: PMC10983808
“Inherited genetic deficiencies in the CD4 receptor present a unique paradigm to study the absolute requirements of this co-receptor in human T helper cell development and function. Researchers extensively characterized the immune profiles of patients with rare mutations causing complete loss of surface CD4 expression, despite the presence of functional MHC class II molecules. By utilizing multi-epitope CD4 antibodies, the study demonstrated that while conventional CD4+ T cells were absent, alternative T cell subsets partially compensated to provide necessary helper functions.”

5. SARS-CoV-2 mRNA vaccination elicits a robust and persistent T follicular helper cell response in humans
Mudd PA, et al. Cell. 2022 Feb 3;185(3):603-613.e15. doi: 10.1016/j.cell.2021.12.026. PMID: 34979117; PMCID: PMC8695127
“The long-term efficacy of SARS-CoV-2 mRNA vaccines is highly dependent on the generation of durable humoral immunity, a process orchestrated by specialized T follicular helper (Tfh) cells. This investigation longitudinally tracked immune responses in vaccinated individuals, revealing a robust and persistent activation of spike-specific Tfh cells within draining lymph nodes. High-dimensional flow cytometry incorporating the human CD4 marker was critical in characterizing the expansion and sustained memory phenotype of these protective T cell populations.”

Syd Labs provides the following in vivo grade recombinant anti-human CD4 monoclonal antibodies:
Clenoliximab biosimilar, research grade, anti-human CD4 monoclonal antibody
Ibalizumab biosimilar, research grade, anti-human CD4 monoclonal antibody
Recombinant Anti-human CD4 monoclonal antibody (Clone: OKT4)
Recombinant Anti-human CD4 monoclonal antibody (Clone: OKT4A)
Recombinant Anti-human CD4 monoclonal antibody (Clone: 13B8.2)
Recombinant Anti-human CD4 monoclonal antibody (Clone: SK3 / Anti-LEU 3a)

Syd Labs provides the following in vivo grade recombinant anti-mouse CD4 monoclonal antibodies:
Recombinant Anti-mouse CD4 monoclonal antibody (Clone: GK1.5)

Syd Labs provides the following recombinant anti-human CD4 monoclonal antibodies for flow cytometry:
Recombinant Anti-human CD4 monoclonal antibody (Clone: OKT4) for flow cytometry
Recombinant Anti-human CD4 monoclonal antibody (Clone: OKT4A) for flow cytometry
Recombinant Anti-human CD4 monoclonal antibody (Clone: 13B8.2) for flow cytometry
Recombinant Anti-human CD4 monoclonal antibody (Clone: SK3 / Anti-LEU 3a) for flow cytometry

Anti-human CD4 (SK3 / Anti-Leu 3a) from: Anti-human CD4 Monoclonal Antibody (Clone: SK3 / Anti-Leu 3a): PA007386.m1 Syd Labs