# Assay of cardiopulmonary bypass system for porcine alveolar macrophages removing GFP-E. coli from erythrocyte surfaces

## TL;DR

This study examines how pig lung macrophages remove bacteria from red blood cells using a specialized system and receptor interactions.

## Contribution

The study introduces a novel assay system to investigate macrophage-erythrocyte interactions in pigs.

## Key findings

- Blocking CR1-like and Fc receptors reduced fluorescence intensity changes in erythrocytes and macrophages.
- PAMs effectively removed GFP-E. coli from erythrocyte surfaces using CR1-like and Fc receptors.
- Transmission electron microscopy confirmed the removal of bacteria from erythrocytes by PAMs.

## Abstract

While it is established that complement receptor molecules on the surface of erythrocytes are crucial for the clearance of immune complexes in the body, the molecular mechanisms underlying the interaction between macrophages and erythrocytes in pigs remain inadequately understood. Consequently, we built a detection system with a closed-circulation flow chamber and a constant flow pump. Additionally, we optimized parameters including system flow velocity and fluid shear force. In the circulatory system, our study measured the fluorescence intensity of erythrocyte and pulmonary alveolar macrophages (PAMs) surfaces before and after the blockade of complement receptor 1 (CR1)-like receptors and Fc receptors. The results indicated that porcine erythrocytes and PAMs exhibited a diminished rate of change in fluorescence intensity under the blocked condition. Through transmission electron microscopy, it was observed that PAMs effectively removed sensitized GFP-E. coli adhering immunologically to porcine erythrocytes. The findings indicate that PAMs effectively removed sensitized GFP-E. coli from the surface immunoadhesion of porcine erythrocytes, facilitated by the mediation of surface CR1-like receptors and Fc receptors.