Soluble Immune Checkpoints in Intra-Abdominal Infections

July 1, 2026 updated by: Ufuk Oguz Idiz, Istanbul Training and Research Hospital

Serum Soluble Immune Checkpoint Molecules in Intra-abdominal Infection: Association With Disease Severity and Mortality

Intraabdominal infections is a life-threatening syndrome with a high incidence and a significant economic burden. The early-stage cytokine storm and the late-stage immunosuppression contribute to the mortality of sepsis. Immune checkpoints expressed on lymphocytes and antigen-presenting cells (APCs) play a crucial role in the pathogenesis of sepsis by regulating immune dysfunction. Specific therapies targeting immune checkpoints have shown great potential in animal and preclinical studies, paving the way for further clinical research. In this study, the significance of serum immune checkpoints - sCD25 (IL-2Ra), 4-1BB, B7.2 (CD86), Free Active TGF-beta1, CTLA-4, PD-L1, PD-1, Tim-3, LAG-3, and Galectin-9 - will be investigated in patients with intraabdominal infection.

Study Overview

Status

Completed

Conditions

Intervention / Treatment

Detailed Description

The abdominal region is the second most common source of sepsis and secondary peritonitis. The most frequent causes of abdominal infections are perforation, ischemic necrosis, or penetrating injuries to intra-abdominal organs. Management consists of infection source control, restoration of gastrointestinal (GI) function, systemic antimicrobial therapy, and support of organ function. Despite advances in care, mortality following secondary peritonitis remains high. Excluding patient-related factors such as age or comorbidities that cannot be influenced during intervention, delays in surgical intervention and failure to achieve source control are the main determinants of outcomes.

Sepsis is defined as life-threatening organ dysfunction caused by a dysregulated host response to infection and accounted for approximately 11 million deaths worldwide in 2017, representing 19.7% of all global deaths. Early deaths in sepsis are typically due to septic shock caused by a cytokine storm. In contrast, late deaths result from the inability to clear primary infections and the development of secondary infections due to a state of immunosuppression.

Multiple mechanisms contribute to immune dysfunction in sepsis. Immune checkpoints, which assist in T cell activation, play critical roles in this process. Immune checkpoint molecules expressed on lymphocytes and antigen-presenting cells (APCs) - including CD28, cytotoxic T-lymphocyte antigen 4 (CTLA-4), CD80, CD86, programmed death-1 (PD-1), and programmed death-ligand 1 (PD-L1) - as well as CD40 and CD40L, OX40 and OX40L, 4-1BB and 4-1BBL, B and T lymphocyte attenuator (BTLA), and the T cell immunoglobulin mucin (Tim) family, serve as co-signaling molecules for T cell activation and immune regulation. Immune checkpoints exert a dual effect on the host response during sepsis. On one hand, during pathogen invasion, immune checkpoints provide critical secondary signals that help APCs activate T cells. Activated T cells and APCs create a positive feedback loop, triggering the cytokine storm. On the other hand, immune checkpoints also regulate T cell activation and inhibition in the late phase of sepsis, leading to T cell anergy and apoptosis.

CTLA-4, also known as CD152, is a competitive receptor for CD28 and plays a negative regulatory role in the immune response of inflammatory diseases by modulating CD28-mediated T cell costimulation. CTLA-4 is also expressed on T regulatory (Treg) cells and temporarily blocks their immune effects. Anti-CTLA-4-based immunotherapy has shown a dose-dependent effect in reducing sepsis-induced apoptosis in a cecal ligation and puncture (CLP) mouse model of sepsis. However, it has minimal effects on inflammatory cytokines.

PD-1, an inhibitory receptor of the CD28 family, is mainly expressed on lymphocytes, dendritic cells (DCs), monocytes, and macrophages. PD-L1, another member of the B7 family and the primary ligand of PD-1, can also be found on lymphocytes, DCs, monocytes, and macrophages. PD-1 and PD-L1 play critical roles in the immunosuppressive state of sepsis and may serve as valuable tools for assessing immune status and as potential therapeutic targets in sepsis. Various studies have confirmed that PD-1, PD-L1, and PD-L2 expression on monocytes and T lymphocytes is increased in septic patients, contributing to a novel immune regulatory system involved in immune dysfunction during sepsis. PD-1 expression on monocytes and T cell repertoire diversity have shown a positive correlation with serum interleukin levels and have been predictive of mortality in patients with septic shock. PD-L1 expression on neutrophils and monocytes has also been associated with risk stratification and mortality in septic patients.

For these reasons, elucidating the roles of immune checkpoints in the pathogenesis of sepsis and the use of immunotherapy hold great potential for sepsis treatment. Although there are limited studies in the literature on the expression of PD-1, PD-L1, PD-L2, and CTLA-4 on T cells and monocytes in sepsis patients, no studies have focused on these markers specifically in intra-abdominal infection patients or on their soluble forms in serum.

Study Type

Observational

Enrollment (Actual)

75

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Locations

  • Turkey (Türkiye)
      • Istanbul, Turkey (Türkiye), 34098
        • Istanbul training and research hospital

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Ages Eligible for Study

  • Adult
  • Older Adult

Accepts Healthy Volunteers

Yes

Sampling Method

Non-Probability Sample

Study Population

Patients with intraabdominal infections due to gastrointestinal pathologies

Description

Inclusion Criteria:

  • Patients with intraabdominal infections due to gastrointestinal pathologies

Exclusion Criteria:

  • Malignities
  • Pregnancy
  • Immune deficiency
  • Patients without intraabdominal infections

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

Cohorts and Interventions

Group / Cohort
Intervention / Treatment
Severe Intraabdominal Infection
Severe Intraabdominal Infection patients with qSOFA 2 and 3
Diagnostic test: Soluble Immune checkpoint levels
Soluble Immune checkpoint levels of the groups before any treatments
Mild Intraabdominal Infection
Mild Intraabdominal Infection patients with qSOFA 0 and 1
Diagnostic test: Soluble Immune checkpoint levels
Soluble Immune checkpoint levels of the groups before any treatments
Control
Healthy Volunteers without intraabdominal infection
Diagnostic test: Soluble Immune checkpoint levels
Soluble Immune checkpoint levels of the groups before any treatments

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Soluble Immune checkpoint levels
Time Frame: December 2023- December 2024
sCD25 (IL-2Ra), 4-1BB, B7.2 (CD86), Free Active TGF-β1, CTLA-4, PD-L1, PD-1, Tim-3, LAG-3, Galectin-9
December 2023- December 2024

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Istanbul Training and Research Hospital

Publications and helpful links

The person responsible for entering information about the study voluntarily provides these publications. These may be about anything related to the study.

General Publications

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Actual)

December 1, 2023

Primary Completion (Actual)

December 31, 2024

Study Completion (Actual)

August 1, 2025

Study Registration Dates

First Submitted

July 1, 2026

First Submitted That Met QC Criteria

July 1, 2026

First Posted (Actual)

July 8, 2026

Study Record Updates

Last Update Posted (Actual)

July 8, 2026

Last Update Submitted That Met QC Criteria

July 1, 2026

Last Verified

July 1, 2026

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

  • Intraabdominal Infections

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

UNDECIDED

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

No

Studies a U.S. FDA-regulated device product

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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