Complement components detected on normal red blood cells taken into EDTA and CPD

Area of Science:

• Immunology
• Hematology

Background:

• Complement system proteins C3 and C4 play crucial roles in immune responses.
• Red blood cells (RBCs) can interact with complement components.
• Understanding these interactions is vital for transfusion medicine and immunology.

Purpose of the Study:

• To investigate the presence and characteristics of bound C3 and C4 subcomponents on normal and stored red blood cells (RBCs).
• To evaluate the impact of fresh normal serum (FNS) incubation on complement component binding to RBCs.

Main Methods:

• Serologic agglutination tests were employed to detect complement subcomponents on RBCs.
• An indirect labeling technique was used for more sensitive detection of bound complement.
• RBCs from fresh EDTA, fresh CPD, and stored CPD blood were analyzed.
• Cells were incubated in compatible fresh normal serum (FNS) at 37°C.

Main Results:

• Serologic tests detected only C3d on untreated RBCs, with increased levels after FNS incubation.
• C3b was detectable only on stored CPD RBCs after FNS incubation.
• Indirect labeling revealed C3d and C4d on all untreated RBC types, with increases after FNS incubation.
• Stored CPD RBCs showed increased C3b binding after FNS incubation; no increase in C4b was observed.

Conclusions:

• Red blood cells possess detectable levels of C3d and C4d, which increase upon incubation with fresh normal serum.
• C3b binding is primarily associated with stored CPD red blood cells, particularly after serum exposure.
• These findings contribute to understanding complement-RBC interactions and their implications.