# Effect of PPD inoculation on serum cytokine profiles in latent tuberculosis infection populations

## TL;DR

This study shows that PPD skin tests cause significant changes in cytokine levels in people with latent tuberculosis compared to healthy individuals.

## Contribution

The study identifies specific cytokines that change significantly after PPD testing in latent tuberculosis infection populations.

## Key findings

- LTBI individuals showed significantly elevated levels of multiple cytokines like β-NGF, IL-10, and IL-6 after PPD testing.
- MCP-1 levels were significantly reduced in LTBI individuals compared to healthy controls after PPD testing.
- Cytokines like G-CSF, MCP-3, and IL-3 increased significantly in LTBI individuals but not in healthy controls.

## Abstract

This study aims to investigate the impact of PPD skin test administration on serum cytokine levels in individuals with latent tuberculosis infection (LTBI) compared to healthy controls. Through quantitative analysis of multiple cytokines in serum samples before and after testing, significant differences were observed in cytokine level changes among LTBI individuals following PPD stimulation. The results indicate that prior to PPD administration, there were no significant differences in cytokine levels between the LTBI group and healthy controls. However, following PPD testing, individuals with LTBI exhibited significantly elevated levels of β-NGF, Eotaxin, G-CSF, GRO-α, IL-10, IL-17A, IL-1α, IL-1β, IL-2, IL-3, IL-4, IL-6, IP-10, LIF, and SDF-1α, while MCP-1 levels were significantly reduced compared to those in healthy controls. Comparative analysis of different population groups before and after PPD skin test administration revealed no significant changes in serum levels of SCGF-β, G-CSF, MCP-3, or IL-3 among healthy controls. In contrast, individuals with latent tuberculosis infection (LTBI) exhibited significantly elevated levels of G-CSF, MCP-3, and IL-3, while SCGF-β levels were markedly reduced. This study provides novel insights into the differential immune responses to PPD testing in latent tuberculosis infection and identifies potential biomarkers for early monitoring of immune activation in tuberculosis infection.