Anti-Mouse NK1.1 [Clone PK136] — Purified in vivo GOLD™ Functional Grade

Clone PK136 is a monoclonal antibody widely used in in vivo mouse studies for the specific depletion of NK (natural killer) cells in mouse strains expressing the NK1.1 (CD161, NKR-P1C) antigen, most notably C57BL/6, FVB/N, NZB, and CE. The antibody binds to NK1.1 on the surface of NK cells and, upon administration (typically via intraperitoneal or intravenous injection), mediates depletion primarily through mechanisms such as antibody-dependent cytotoxicity or phagocytosis.

Key details on usage in in vivo studies:

• Primary Application: PK136 is most commonly used to functionally deplete NK cells in vivo, allowing researchers to assess the role of NK cells in immunity, infection, cancer, transplantation tolerance, and other physiological or pathological processes.
• Experimental Models: The antibody is used in mouse strains that naturally express the NK1.1 antigen (e.g., C57BL/6), as not all strains have this marker.
• Typical Protocol: Depletion is typically achieved by intraperitoneal injection of PK136. The dosage and frequency vary, but studies often use doses in the range of 100–200 ?g per mouse, given 1–3 days before experimental analysis and, if required, repeated at intervals to maintain NK cell depletion.
• Validation: The effectiveness of depletion can be confirmed by flow cytometry using non-competing NK cell markers.
• Off-target Effects: While PK136 is highly specific, it may also label rare subsets of T cells or monocytes in some strains, so off-target depletion should be considered in experimental design.
• Other Uses: While the main use in vivo is depletion, PK136 is also used for identification (e.g., flow cytometry) and in vitro activation studies.

Summary table:

Citations:

• Depletion protocol and specificity
• Strain restriction
• Mechanism and validation

Commonly used antibodies or proteins in the literature that are used alongside PK136 (anti-NK1.1) include other immune cell markers, NK cell markers, and depletion or blocking antibodies to define cell populations and manipulate NK cells in mice. The most frequently used are:

• Anti-CD3e (clone 145-2C11): Used to distinguish NK cells (NK1.1+ CD3-) from NKT cells (NK1.1+ CD3+) in flow cytometry. This is a standard marker for T cells in mice and enables clear separation of NK, NKT, and T cell compartments when combined with PK136.

• Anti-CD49b (clone DX5): Another pan-NK cell marker in mice. DX5 is especially useful in mouse strains that do not express NK1.1; in strains that do, it is often used together with PK136 to confirm NK cell identity or for functional depletion.

• Anti-Asialo GM1 (polyclonal): Used for NK cell depletion in vivo, targeting the asialo GM1 glycolipid which is highly expressed on NK cells. Sometimes used as an alternative to or in combination with PK136 for NK cell depletion experiments.

• Anti-NKp46 (clone 29A1.4): NKp46 is another NK cell marker present across multiple species, including mice. This antibody is often included in multi-parameter flow panels for more precise identification or isolation of NK cells.

• Anti-CD56 (human studies, clone B159): Not applicable to mice, but commonly cited in comparative studies for human NK cell identification and depletion.

• Anti-mouse IgG2a (clone R19-15): Used as a secondary antibody in flow cytometry when PK136 is not conjugated, enabling detection of the primary antibody via fluorescence-labeled anti-IgG2a.

Other frequently co-used reagents (depending on experimental goal):

• Isotype controls: Such as mouse IgG2a for specificity controls.
• Cytokines (e.g., IL-2): Sometimes co-administered for NK cell activation in functional experiments with plate-bound PK136.

In summary, anti-CD3e, anti-CD49b (DX5), and anti-Asialo GM1 are the most common antibodies used alongside PK136 for NK cell identification and functional studies in mice.

Clone PK136 is a monoclonal antibody widely used in immunology research for the recognition and depletion of NK1.1 (CD161, NKR-P1C, Ly-55), a surface antigen expressed by natural killer (NK) cells and a subset of T cells in certain mouse strains.

Key findings from scientific literature citing clone PK136 include:

• Highly Specific NK1.1 Detection: PK136 binds specifically to NK1.1, reliably identifying NK cells (NK1.1? CD3e?) and NKT cells (NK1.1^dim CD3e?), enabling precise analysis by flow cytometry in mouse strains expressing this epitope, such as C57BL/6, FVB/N, NZB, and CE. It does not react with all mouse strains—for example, it does not detect NK cells from 129, BALB/c, A, AKR, C3H, CBA, or SJL mice.

• Efficient Depletion of NK Cells: Treatment with PK136 effectively depletes NK1.1? cells in vivo, demonstrated by a notable reduction in NK1.1-expressing spleen cells and strongly reduced NK activity in cytotoxicity assays. For instance, a single injection reduced NK1.1? spleen cells from 5.5% to 0.6%, and corresponding cytotoxicity decreased from 21% in controls to 3.3% at an effector/target ratio of 200:1. This depletion is widely used to assess the role of NK cells in infection, cancer, and autoimmunity models.

• Experimental Flexibility and Use: PK136 is suitable for multiple methods: flow cytometry, immunoprecipitation, immunohistochemistry, and immunofluorescence. Its high specificity and efficiency make it a valuable tool for in vivo NK cell depletion, with dosing adjusted according to experimental context.

• NK1.1 Antigen Distribution: PK136 has clarified that only a minor fraction of T cells are NK1.1 positive (?0.5% of CD4? or CD8? splenocytes), supporting the separation of canonical NK and NKT cell populations in studies using this marker. PK136 thus helps distinguish between NK, NKT, and classical T cells in immunophenotyping experiments.

• Caveats and Limitations: The use of PK136 must be limited to appropriate mouse strains (primarily those with the NK1.1 epitope present) and requires careful interpretation when using strains where this marker is absent or when alternative depletion strategies are necessary.

• Historical and Methodological Reviews: PK136 was described in foundational work by Koo and Peppard in 1984, leading to widespread use for dissecting NK cell function and development in murine systems.

In summary, clone PK136 is recognized as the benchmark monoclonal antibody for NK1.1 detection and depletion in vivo and in vitro in susceptible mouse strains, enabling mechanistic studies on the role of NK and NKT cells in immunity and disease.

Dosing regimens of clone PK136 (anti-NK1.1) for NK cell depletion in mice typically range from 200–500 ?g per mouse per injection, with schedules and doses varying according to mouse strain, experimental goals, and depletion duration.

Key dosing strategies across studies and mouse models:

• Standard regimen: 200–300 ?g per mouse, administered via intraperitoneal injection, 1–3 times per week as needed.
• Single dose model: A one-time injection of 200 ?g is sufficient for acute depletion in most models.
• Repeated/sustained depletion: 200 ?g every 3–5 days, or up to three times per week for ongoing depletion.
• Initial higher dose with maintenance: Start with 250 ?g, then continue with 100–150 ?g every 3–5 days for prolonged studies.

Important factors influencing dosing:

• Mouse strain: NK1.1 is predominantly found in C57BL/6 and some related mouse strains; dosing for PK136 is most effective in these models.
• Experimental purpose: Acute depletion often uses single/short-term dosing; chronic studies require higher and/or repeated doses with careful monitoring for immune responses or variable depletion efficiency.
• Other variables: Age, health status, and experimental context (e.g., infection vs. tumor models) may necessitate dose adjustment.

Drawbacks and considerations:

• PK136 may occasionally bind non-target cells, leading to off-target effects.
• Depletion efficiency and immune response to repeated antibody administration can vary, particularly with prolonged use.

In summary, PK136 dosing regimens are customized according to strain, application, and duration, but most commonly employ 200–300 ?g i.p. injections 1–3 times weekly for robust NK cell depletion in C57BL/6 mice and similar strains.