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Animal data onlyimmuneinflammationcognition

Tuftsin

An IgG-derived tetrapeptide that switches macrophages and microglia toward active phagocytosis, and the structural parent of the anxiolytic peptide Selank.

Also known as Thr-Lys-Pro-Arg, TKPR, IgG heavy chain 289-292

Animal data only — Rodent or other animal studies. Dose translation to humans is genuinely uncertain.

Well-characterised biology dating to its 1970 discovery, with a clear physiological role and a defined receptor, but essentially no human therapeutic trials. Most modern research uses tuftsin as a targeting ligand for drug delivery rather than as a therapeutic itself.

How it works

Tuftsin is cleaved enzymatically from residues 289-292 of the IgG heavy chain in the spleen, which is why splenectomy produces a tuftsin-deficiency state. It acts on macrophages, monocytes, neutrophils and microglia to increase phagocytic uptake, chemotaxis, antigen presentation and bactericidal activity; neuropilin-1 has been identified as a principal binding partner. In the CNS, tuftsin signalling through Nrp1 on microglia shifts them toward an anti-inflammatory M2-like phenotype, which is the basis for interest in it for multiple sclerosis and neuroinflammation models. Its clinical footprint is almost entirely as a delivery scaffold and as the parent structure of Selank rather than as a drug in its own right.

Targets: Neuropilin-1, Macrophage/microglial phagocytosis, Neutrophil chemotaxis

Dosing

ProtocolDoseFrequencyRoute
Research-use protocolNo established timing.100 mcg – 500 mcgonce dailysubcutaneous
  • · There is no validated human dose. This range comes from research-supplier convention scaled off rodent studies, not from trials. If you want tuftsin-adjacent effects with actual clinical history behind them, Selank is the better-characterised option.

Cycling

No established cycle. Users typically run short two-to-four-week blocks purely because nothing longer has ever been studied.

Work out your exact syringe units →

Pharmacology

Half-life
Short - a tetrapeptide cleared within minutes by serum peptidases. No human pharmacokinetic data of substance.
Onset
Not characterised in humans.
Routes
subcutaneous, intranasal
Molecule
Endogenous tetrapeptide (IgG Fc fragment)
Sequence length
4 amino acids
Molecular weight
500.6 Da

Handling

Diluent
Bacteriostatic water
Typical mix
2 or 3 mL
Vial sizes
5, 10 mg
Lyophilised
Room temperature short term; fridge or freezer long term.
Reconstituted
Refrigerated, use within about 30 days.
Light sensitive
Yes — keep it out of the light

Intranasal — usable, with a caveat

Intranasal use follows from the Russian work on this tetrapeptide and from Selank, which is its stabilised analogue and is genuinely a nasal drug. Tuftsin itself has no modern human pharmacokinetic data by the nasal route.

Mixing

A 10 mg vial in 2 mL gives 5 mg/mL; 250 mcg is 5 units on a U-100 syringe.

Side effects

  • commonInjection-site irritation
  • commonUnknown safety profile— No human safety dataset exists.
  • rareTheoretical pro-inflammatory flare— Activating phagocytes is not automatically desirable in someone with existing inflammatory disease.

Do not use if

  • Active autoimmune or strongly inflammatory disease, where further macrophage activation may be counterproductive.

Combining it

  • redundantselank — Selank is a stabilised tuftsin analogue with actual clinical registration behind it.
  • conflictImmunosuppressants — Opposing pharmacology.

What to monitor

  • · CBC with differential if used for any length of time.
  • · Inflammatory markers such as CRP if you have an inflammatory condition.

Legal status

Not approved anywhere; research chemical only.

References

  • Najjar and Nishioka 1970, tuftsin: a natural phagocytosis-stimulating peptide (Nature) (preclinical)
  • Tuftsin-neuropilin-1 signalling in microglia and experimental autoimmune encephalomyelitis (preclinical)

Mechanism in depth

The receptor question was open for four decades and has a real answer now: neuropilin-1. Nissen and colleagues showed in Glia in 2016 that tuftsin-driven recovery in experimental autoimmune encephalomyelitis requires Nrp1, using conditional knockouts rather than pharmacological inference. What tuftsin does through Nrp1 on microglia is the interesting part, and it is not what the classical macrophage-activation framing predicts. In the CNS, tuftsin-Nrp1 signalling drives microglia toward an anti-inflammatory, M2-like phenotype and promotes regulatory T-cell induction via TGF-beta - so in neuroinflammation the peptide is immunosuppressive in effect, not stimulatory. In the periphery, on macrophages, monocytes and neutrophils, the classical description holds: increased phagocytic uptake, chemotaxis, antigen presentation and bactericidal killing. So the same molecule reads as an immune activator in a peritoneal macrophage assay and as an immune damper in an EAE model. That is not a contradiction, it is cell-context dependence, and it is the single most important thing to understand before deciding what you expect tuftsin to do to you - because the answer depends entirely on which compartment you are asking about. The other point worth being blunt about: the overwhelming majority of modern tuftsin publications use it as a targeting ligand to deliver something else to macrophages, not as a therapeutic in its own right.

What usually goes wrong

The main thing that goes wrong is that nothing happens and you have no way to detect whether it did, because there is no human dose, no human pharmacokinetics and no biomarker. The predictable harm is the mirror image of the intended effect: activating peripheral macrophages in someone with an existing inflammatory or autoimmune condition is pushing in the wrong direction, and a CRP rise with worsening symptoms two to four weeks in is exactly the pattern to watch for. The specific confusion worth naming is people reading the neuroinflammation literature - where tuftsin is anti-inflammatory via Nrp1 on microglia - and assuming that generalises to systemic use. It does not. Finally, the 100-500 mcg daily figure in circulation is supplier convention scaled from rodent work; nobody has established a human dose and nobody has run a dose-ranging study.

Bloodwork worth running

MarkerWhenWhy it matters
CBC with differentialBaseline and at the end of a two to four week block.Baseline and safety. Tuftsin's stated action is on the phagocyte compartment, so the neutrophil and monocyte counts are the relevant lines.Act if: No established threshold.
hs-CRPBaseline and at two to four weeks, and again if symptoms change.The one genuinely predictable risk with this compound is driving inflammation upward in someone who already has an inflammatory condition, since peripheral macrophage activation is the classical effect.Act if: A sustained rise from a normal baseline is a reason to stop rather than push through.
Immunoglobulin G level, only if you have had a splenectomy or aspleniaBaseline, as part of an asplenia workup rather than as monitoring.Tuftsin deficiency is a real, defined clinical state in asplenia because the spleen is where the peptide is cleaved from IgG. That is the one population where a rationale for replacement exists at all.

Pharmacokinetics

Metabolism
Serum aminopeptidase and carboxypeptidase cleavage. Notably, removal of the N-terminal threonine yields Lys-Pro-Arg, which is not simply inactive - fragments of tuftsin have their own reported activity, so degradation is not a clean off-switch.
Elimination
Amino acid recycling.

Receptor targets

  • Neuropilin-1 (Nrp1) — No Kd published for the tuftsin-Nrp1 interaction. Nrp1 binds C-terminal arginine motifs, which is consistent with tuftsin's C-terminal Arg, but the affinity has not been quantified in the accessible literature.

    On microglia, drives an anti-inflammatory M2-like polarisation and TGF-beta-dependent regulatory T-cell induction. Genetically required for tuftsin-driven EAE recovery.

  • Macrophage and monocyte phagocytic machinery — Not quantified

    Increased phagocytic uptake, chemotaxis, antigen presentation and bactericidal activity. This is the classical 1970s description and it applies to peripheral phagocytes.

  • Neutrophil chemotaxis — Not quantified

    Enhanced directional migration.

What to expect, and when

Minutes: the peptide is degraded. Hours to days: no reliable human onset data exist at any timescale. In rodent phagocytosis assays the functional effect on macrophages is acute, within hours of exposure. Weeks 2-4: the length of block most users run, chosen because nothing longer has ever been studied rather than because anything is expected to happen at four weeks. There is no established timeline for this compound in people, and any specific one you are given is invented.

Stacking and comparisons

The honest advice is that if you want tuftsin's pharmacology you should probably take Selank instead. Selank is tuftsin with a Pro-Gly-Pro tail bolted on specifically to survive peptidases, and it has actual Russian clinical registration and human trial data behind it, which native tuftsin does not. Stacking tuftsin with Selank is redundant. Combining it with anything immunosuppressive is pharmacologically incoherent in the periphery, though the Nrp1-microglial arm muddies even that. The one combination with a coherent rationale is with an antimicrobial host-defence peptide like LL-37 - tuftsin increases phagocyte uptake and killing, LL-37 permeabilises the organism - but there is no human data on it whatsoever.

Tuftsin is the classic example of a peptide with excellent biology and no therapeutic career. Its receptor is identified, its physiological role is defined, splenectomy produces a genuine deficiency state - and it has essentially no human trials, because a tetrapeptide with a minutes-long half-life is not a drug. The field's answer to that was Selank, which is what you should be comparing against: same parent structure, protected against degradation, actual clinical registration in Russia, real anxiolytic and immunomodulatory human data. Within this class, tuftsin sits alongside alpha-MSH as a compound whose stabilised derivative is the useful thing and whose native form is mostly of historical and mechanistic interest. Against LL-37 and the defensins it is a different mechanism entirely - tuftsin makes your phagocytes work harder, host-defence peptides kill organisms directly.

Rough cost

$40–$100/month. A 10 mg vial covers roughly a month at 250-500 mcg daily. Typical research-supplier pricing; not a verified vendor survey.

Genuinely uncertain

  • No human pharmacokinetic data of substance exist. Tmax, bioavailability, volume of distribution, clearance and half-life are all unpublished.
  • No binding affinity has been published for the tuftsin-neuropilin-1 interaction despite Nrp1 being genetically established as required.
  • The 100-500 mcg daily dose range is supplier convention scaled from rodent studies with no human dose-ranging behind it.
  • Whether tuftsin crosses the blood-brain barrier after peripheral administration is unresolved. The microglial effects are established in models where CNS access was not the limiting question.
  • The relationship between the peripheral pro-phagocytic effect and the central anti-inflammatory effect has not been characterised in a single system, so which dominates after a subcutaneous dose in a human is unknown.
  • No human therapeutic trial has ever been conducted, so the trials array is genuinely empty.

Papers