Immune

Glutathione (GSH) is a tripeptide composed of glutamate, cysteine, and glycine, linked by an unusual gamma peptide bond between the gamma-carboxyl group of glutamate and the amino group of cysteine. It is the most abundant non-protein thiol in mammalian cells, with intracellular concentrations ranging from 1-10 mM. Present in virtually every cell in the body, it functions as the principal intracellular antioxidant and plays critical roles in detoxification, immune function, and cellular homeostasis. Unlike most peptides discussed in research databases, glutathione is an endogenous compound with well-established biochemistry. Its clinical relevance stems from the observation that glutathione levels decline with age and are depleted in numerous disease states including HIV/AIDS, liver disease, neurodegenerative disorders, and pulmonary conditions. Exogenous supplementation strategies — including direct administration, precursor supplementation (NAC), and liposomal delivery — are areas of active clinical investigation.

KPV (Lys-Pro-Val) is a naturally occurring tripeptide corresponding to the C-terminal fragment (residues 11-13) of alpha-melanocyte-stimulating hormone (α-MSH). Despite being only three amino acids, KPV retains the potent anti-inflammatory activity of the full 13-amino acid α-MSH peptide while lacking its melanogenic (tanning) and hormonal effects. This dissociation of anti-inflammatory activity from melanocortin receptor-mediated effects makes KPV an attractive candidate for inflammatory conditions where pigmentation changes would be an unwanted side effect. KPV has been studied primarily in the context of intestinal inflammation and skin disorders, with preclinical data showing efficacy in colitis models and dermatitis. Its small molecular size (342 Da) offers practical advantages — oral bioavailability, skin penetration, and low manufacturing cost relative to larger peptides. The peptide is part of a broader research effort to identify the minimal active fragments of endogenous anti-inflammatory peptides for therapeutic development.

Thymosin Alpha-1 (Tα1) is a 28-amino acid peptide originally isolated from thymic tissue (Thymosin Fraction 5) by Allan Goldstein at George Washington University in the 1970s. It is an N-terminally acetylated peptide that plays a central role in T-cell maturation and immune system regulation. The synthetic form, marketed as thymalfasin (Zadaxin), is approved in over 35 countries for the treatment of chronic hepatitis B and as an immune adjuvant, though it does not have FDA approval in the United States. Tα1 occupies a distinctive position in peptide therapeutics as one of the few immunomodulatory peptides with extensive clinical trial data and regulatory approval in multiple jurisdictions. It has been studied in over 4,400 patients across clinical trials for hepatitis B, hepatitis C, certain cancers, HIV/AIDS, and vaccine enhancement in immunocompromised populations. Its mechanism of action involves enhancement of innate and adaptive immunity through dendritic cell maturation and T-cell differentiation, while simultaneously promoting immune tolerance through separate regulatory pathways.

Thymulin (originally named Facteur Thymique Sérique, or Serum Thymic Factor) is a nonapeptide exclusively produced by thymic epithelial cells, discovered by Jean-François Bach at the Hôpital Necker in Paris in the 1970s. It is unique among thymic peptides in its absolute requirement for zinc — the apo-peptide (without zinc) is biologically inactive, and only the zinc-coordinated form can bind to its receptor and exert immunomodulatory effects. The zinc ion is coordinated by the asparagine, serine, and glutamine residues in the C-terminal portion of the molecule. Thymulin levels in circulation decline dramatically with age, paralleling the involution of the thymus gland. Peak levels occur during puberty and decrease to near-undetectable concentrations by age 60. This decline correlates with the age-related deterioration of T-cell-mediated immunity (immunosenescence), making thymulin a biomarker of thymic function and a candidate therapeutic for restoring immune competence in aging. Its zinc dependency also connects thymulin biology to the well-documented effects of zinc deficiency on immune function.