Anti-Mouse CD4 (Clone YTS191) – Purified in vivo PLATINUM™ Functional Grade

Clone YTS191 is most commonly used in vivo in mice for the targeted depletion of CD4⁺ T cells. This application allows researchers to study the roles of CD4⁺ T cells in immune responses, disease models, and therapeutic interventions.

Key in vivo applications include:

• CD4⁺ T cell depletion: YTS191 is administered to mice to selectively and effectively deplete CD4⁺ T cells, which are critical in immune regulation and pathology.
• Functional immune studies: By depleting CD4⁺ T cells, researchers can dissect their roles in health (e.g., homeostasis, immune surveillance), in disease settings (e.g., autoimmunity, infection, cancer), and during therapeutic interventions (e.g., transplantation, immune checkpoint blockade).
• Multiplexed immune cell depletion: YTS191 is sometimes used in combination with other depleting antibodies to study complex immune cell interactions, such as dual depletion of CD4⁺ and CD8⁺ T cells.
• Assessment of CD4⁺ populations: Besides depletion, YTS191 is also used for flow cytometry and immunohistochemistry to track and quantify CD4 expression in vivo and ex vivo, but depletion remains the primary in vivo application.

Supporting details:

• Target specificity: YTS191 targets the CD4 molecule, expressed on most thymocytes, MHC class II-restricted T cells (helper T cells), subsets of NKT cells, dendritic cells, and macrophages.
• Compatibility: The antibody is formulated to minimize endotoxin contamination for in vivo use to reduce confounding inflammatory effects during experiments.
• Comparison to other clones: It is functionally similar to other anti-CD4 depleting clones, such as GK1.5 and YTS177, but is chosen in some protocols based on strain compatibility, epitope recognition, or cross-reactivity.

Less common or alternative in vivo uses may include studying the involvement of CD4⁺ cells in central nervous system diseases through their depletion, but such applications are typically model-specific and less broadly reported.

In summary, clone YTS191 is a standard tool for in vivo depletion of CD4⁺ T cells in mice, enabling exploration of CD4-mediated immune mechanisms in numerous disease and therapeutic models.

The most commonly used antibodies or proteins alongside YTS191 in the literature are those targeting CD8, CD25, Gr-1, NK1.1, and myeloid markers. Researchers frequently use these antibodies to distinguish or deplete specific immune cell subsets depending on the experimental context, such as in immunology and T cell subset depletion studies.

Relevant details:

• CD8 (often clone KT15): Used for depleting or detecting cytotoxic T cells; dual-color flow cytometry setups commonly employ YTS191 for CD4 and KT15 for CD8.
• CD25: Marks regulatory T cells, used for subset distinction.
• Gr-1 (Ly6G/Ly6C): Marks myeloid cells (e.g., neutrophils) for depletion or analysis.
• NK1.1: For identifying or depleting NK cells.
• Myeloid markers (e.g., F4/80, CD11b): Often used to characterize and sort macrophages and monocytes.

Alternative and related antibodies:

• GK1.5: Another anti-mouse CD4 antibody clone, often compared with YTS191 for similar applications.
• YTS177: Competes for CD4 binding like YTS191 and is cited in comparative studies.
• Isotype controls: Such as rat IgG2b, to confirm specificity in experimental setups.

These combinations facilitate depletion experiments, immune subset analysis, and checkpoint inhibitor studies, reflecting common practice in murine immunological research.

Clone YTS191 is a rat monoclonal antibody that specifically recognizes mouse CD4, and scientific literature reveals several important findings about its applications and mechanisms in immunological research.

Target Specificity and Cell Recognition

YTS191 recognizes an epitope on murine CD4, a 58 kDa type I transmembrane glycoprotein of the immunoglobulin superfamily. The antibody facilitates identification and isolation of CD4+ T cell populations, which include helper T cells, immunosuppressive regulatory T cells (Tregs), and subsets of natural killer T cells, dendritic cells, and macrophages.

In Vivo Depletion Capabilities

A major finding demonstrates that YTS191 exhibits potent depleting activity when administered in vivo. The antibody is commonly used at doses of 200 μg administered intraperitoneally for effective CD4+ T cell depletion in mouse models. Importantly, the fluorochrome-labeled anti-CD4 mAb clone RM4-5 used for flow cytometry analyses differs from YTS191, allowing researchers to track CD4+ cells even after depletion with YTS191.

Therapeutic Protection Mechanisms

Research involving the bacterial enzyme CU43 revealed critical insights into antibody-mediated immune protection. Studies demonstrated that wild-type CU43, formulated as an Fc fusion protein, could protect mice humanized for Fcγ receptors from YTS191-mediated cytotoxic depletion of CD4+ T cells by defeating antibody Fc effector functions. This protection required CU43 to both bind the IgG N297-linked glycan and maintain protein-protein interactions with the Fc substrate. Mutant variants of CU43 that lost either glycan recognition (CU43^Q260A-Y262A^ and CU43^E294A-E295A^) or protein binding capability (CU43^R200A-W201A-R204A^) were completely incapable of preventing CD4+ T cell depletion.

Immune Checkpoint Therapy Studies

YTS191 has been instrumental in dissecting mechanisms of immune checkpoint inhibitor combinations. In studies examining anti-PD-1 therapy combined with either anti-CTLA-4 or anti-LAG-3, CD4+ T cell depletion using YTS191 revealed differential dependencies on CD4+ T cells. Specifically, depleting CD4+ cells led to an 89% decrease in IFNγ release from immune cells in anti-PD-1+LAG-3 treated tumors, suggesting this combination relies on T helper function. Conversely, CD4+ T cell depletion in anti-PD-1+CTLA-4 treated mice resulted in a 110% increase in IFNγ release, indicating suppression of Treg activity.

Competitive Binding Studies

YTS191 competes with other anti-CD4 antibodies, including clones YTS177 and GK1.5, for CD4 binding. This competitive relationship has been exploited in experimental designs where multiple depleting antibodies are used together, with researchers often administering both YTS191 and GK1.5 simultaneously at 200 μg each to ensure complete CD4+ T cell depletion.

Thymopoiesis Research

Studies investigating thymic reconstitution after lymphoablation have utilized YTS191 to examine the role of peripheral CD4+ T cells in thymopoiesis. These experiments demonstrated cooperation between the thymus and peripheral CD4+ T cells in ensuring optimal T cell reconstitution following lymphoablative therapy.

The dosing regimens of clone YTS191, a rat anti-mouse CD4 monoclonal antibody, show notable variation across mouse models in both dose amount and schedule, largely depending on experimental objectives and mouse strain.

Key variations observed:

• Standard Depletion Regimens:
  • In C3H/HeNCrl mice, YTS191 is commonly administered at 100 μg/injection intraperitoneally (i.p.), three days before tumor cell injection, then every 4 days thereafter for the duration of the experiment.
• Low-Dose, Rapid Depletion Studies:
  • In FcγR humanized mice, considerably lower doses of 10 μg/mouse intravenously (i.v.) have been used, typically with sampling to assess CD4+ T cell depletion at days 0, 1, and 3 after administration.
• Published Dose Ranges:
  • Vendor and summary resources indicate that dosing can generally range from 10 μg to over 100 μg per mouse, and the route may be either i.p. or i.v. depending on immune depletion stringency and experimental design.

Example Dosing Table:

Influencing Factors:

• Mouse strain (susceptibility and immunocompetence)
• Experimental goal: Tumor immunology, infectious disease, acute vs. chronic depletion
• Route of administration: i.p. for routine depletion, i.v. for immediate systemic effects

Dosing regimens should always be tailored based on objective, model, and pilot studies, but most reported protocols in the literature fall within the 10–100 μg/mouse range, delivered i.p. or i.v., with injection intervals ranging from every 3 to every 7 days.

References directly supporting these details:

• Intraperitoneal 100 μg dosing in C3H/HeNCrl mice for immunodepletion.
• Intravenous 10 μg dosing in FcγR humanized mice for acute depletion.
• Broad vendor information confirming dose range (10–100 μg or higher), variable by context.

If a specific disease model or mouse strain is of interest, refinements in dosing based on published optimization studies should be considered.