Clone PK136 is most commonly used in vivo in mice for the specific depletion (removal) of natural killer (NK) cells in strains expressing the NK1.1 (CD161, NKRP1C) antigen, such as C57BL/6, FVB/N, NZB, and CE.

Essential context and supporting details:

• Primary Application:
  The most cited and extensively validated in vivo use is NK cell depletion, which allows researchers to study the function of NK cells in various biological processes, including infection, tumor surveillance, autoimmunity, and graft rejection.

• Additional In Vivo Uses:

  • Functional blocking/neutralization: PK136 is sometimes used in vivo to block NK1.1 activity, allowing for studies of receptor signaling or inhibition of cytotoxic activity.
  • Investigation of disease mechanisms: By removing NK cells, researchers can assess how this affects outcomes in models of cancer, viral infection, or autoimmune disease.
  • Evaluation of immune cell interactions: In models where NKT or certain T cell subsets also express NK1.1, PK136 can partially deplete or label these populations, but the primary use is still NK cell targeting.

Common Strains and Specificity:

• PK136 is strainspecific and effective mainly in strains expressing the NK1.1 (CD161b or c) antigen (e.g., C57BL/6, FVB/N, NZB, and CE). Not effective in BALB/c or AKR mice, which do not express NK1.1.

Experimental Considerations:

• Dosing: Protocols typically employ a single or repeated intraperitoneal dose ranging from 200–250 μg per mouse, sometimes followed by maintenance doses for sustained depletion.
• Potential pitfalls: PK136 may show variable effectiveness depending on animal strain and experimental setting. Rare offtarget effects are possible due to the complexity of NK1.1 expression (some T cells and monocytes may be labeled in specific contexts).

Summary Table: Common In Vivo Applications of Clone PK136 in Mice

Key references emphasize that NK cell depletion is the most reliable and frequent in vivo application in experimental immunology using mouse models.

The most commonly used antibodies or proteins alongside PK136 in the literature are antiCD3e, antiCD49b (DX5), and antiAsialo GM1. These are frequently employed in NK cell identification, functional studies, and depletion experiments using mouse models.

Key antibodies and proteins often used with PK136:

• AntiCD3e: Used to mark and exclude T cells in flow cytometry or functional assays, allowing clear identification of NK cells.
• AntiCD49b (DX5): Labels NK cells and is especially valuable in mouse strains not expressing NK1.1 (target of PK136).
• AntiAsialo GM1: Used for depleting NK cells in vivo and sometimes in functional assays.
• AntiNKp46 (clone 29A1.4): Another marker for NK cells, useful for additional identification or depletion strategies across species.
• AntiCD56 (human studies): Human NK cell marker (clone B159), used in human studies since PK136 is specific to mouse.

Other reagents sometimes seen with PK136:

• Mouse IgG isotype controls: For specificity controls (e.g., mouse IgG2a).
• Myeloid and T cell markers: Such as antiCD8, antiCD4, or antiCD11b in broader immunophenotyping panels.
• Tolllike receptor ligands (e.g., LPS, Pam3CSK4): Used in functional or depletion experiments to modulate immune responses.

Summary of usage:

• In flow cytometry, PK136 is often paired with DX5 and CD3e to distinguish NK cells precisely.
• For in vivo depletion, PK136, Asialo GM1, or DX5 may be compared for efficiency and specificity.
• In specific models or mouse strains where NK1.1 is absent, DX5 is recommended.

These combinations enable robust identification, depletion, and study of NK cells in mouse immunology research. The precise selection depends on the experimental design, mouse strain, and whether the goal is identification, depletion, or functional modulation.

Clone PK136 is a mouse monoclonal antibody that binds specifically to NK1.1, a cell surface antigen expressed predominantly on mouse natural killer (NK) cells and a subset of T cells in certain mouse strains. The major scientific findings from literature that cite clone PK136 can be summarized as follows:

• Highly Specific NK1.1 Detection: PK136 reliably identifies NK1.1+ cells, which include NK cells and some NKT cells.

• Efficient NK Cell Depletion: PK136 is routinely used in vivo to selectively deplete NK cells in experimental mouse models. Depletion is efficient, helping elucidate the functional roles of NK cells in immunity, cancer, infection, and autoimmunity.

• Strain Specificity: NK1.1 is only expressed on NK cells from specific mouse strains (such as C57BL/6, FVB/N, NZB, and CE); therefore, PK136 is effective only in these strains and not in others (like 129, BALB/c, C3H, and SJL).

• Flow Cytometry Applications: PK136 is a gold standard for flow cytometric analysis to distinguish between NK cells (NK1.1+ CD3) and NKT cells (NK1.1[dim] CD3+).

• Experimental Versatility: PK136 is used in various immunological assays, including immunoprecipitation, immunohistochemistry, and immunofluorescence, providing broad utility in basic and translational research.

• Offtarget and Aspecific Binding Risk: Studies have reported that PK136 may exhibit aspecific binding to nonNK cells—particularly myeloid cells—leading to potential confounding effects in experimental outcomes, especially in certain strains and assay conditions.

• Functional Consequences of NK Cell Depletion: Depletion of NK1.1+ cells with PK136 has been shown to enhance the effectiveness of other immune cells (e.g., CD4+ T cells) against tumors in mice, demonstrating PK136's utility in dissecting immune cell interactions.

• Dosing Regimens: Typical in vivo dosing involves 200–250 μg per mouse via intraperitoneal injection, with maintenance doses for sustained depletion. Dosing must be optimized depending on experiment type and strain.

• Limitations: Prolonged or repeated use can lead to immune responses against the antibody, and the efficiency of depletion may vary across experiments and mouse strains.

In science, clone PK136 is recognized for its specificity, efficiency, and utility in marking or depleting NK cells, which has significantly advanced the study of immune responses in mice. However, careful consideration of strain specificity, dosing, and potential offtarget effects is required for experimental design.

Dosing regimens of the antiNK1.1 antibody clone PK136 in mouse models typically range from 200 to 500 μg per mouse per dose, most often delivered by intraperitoneal injection, with schedules and doses varying according to mouse strain, experimental goal, and desired depletion duration.

Key dosing regimens for PK136 include:

• Single dose: Often 200 μg per mouse by intraperitoneal injection, used for shortterm or initial depletion of NK cells, most commonly in NK1.1positive strains such as C57BL/6.
• Repeated doses: 200 μg per mouse every 3–5 days allows for sustained NK cell depletion, suitable for experiments requiring longerterm immune manipulation.
• Initial high dose: Some protocols start with 250 μg per mouse, followed by maintenance doses of 100–150 μg every 3–5 days for ongoing depletion.
• Highintensity depletion: For certain models or longterm studies, higher doses such as 500 μg per mouse, administered three times a week, have been used, with significant NK and NKT cell removal confirmed by FACS analysis.

Factors influencing dosing variation:

• Mouse strain: NK1.1 is primarily expressed in strains like C57BL/6, FVB/N, and related lines. Other strains may require alternative strategies or different antibodies, as PK136 only depletes NK1.1^+^ cells.
• Experimental aim and cell target: For NK cell depletion, the above regimens are standard. If NKT cell removal is also required, dosing confirmation by flow cytometry is necessary, as the efficiency of depletion may differ.
• Duration and immune response: Repeated dosing can provoke antiantibody immune responses, causing possible loss of efficacy over time, so schedules should be adjusted or monitored accordingly.
• Age and disease model: Younger or immunocompromised mice might require lower doses due to altered pharmacokinetics and immune function.

Supporting details:

• PK136 is highly specific to NK1.1, reducing offtarget effects, but depletion efficacy can vary between experiments and strains.
• Standard administration route is intraperitoneal (i.p.) for both acute and chronic studies.
• Confirmatory monitoring of NK cell depletion typically involves flow cytometry using additional NK markers postantibody administration.

In summary, while 200–300 μg/mouse i.p., 1–3 times per week is the most widely used regimen, optimal dosing depends on strain, age, experimental design, and depletion duration, with some models requiring initial higher doses or more frequent administration for complete NK or NKT cell removal.