Introduction. CD30, member of the TNF-receptor family, is expressed on activated T and B cells and is cleaved by a metalloprotease following CD30 signaling, but the function of CD30 remains elusive. CD30 was initially described on the surface of Reed-Sternberg cells, and elevated levels of soluble CD30 (sCD30) have been described in patients with lymphoma, HIV and autoimmune diseases. Higher levels have been associated with unfavorable prognosis in lymphoma and HIV, and are thought to represent a Th2-polarized response. Relatively little is known about sCD30 profiles in many hematologic disorders.
Method. We measured plasma sCD30 levels in patients with 1) non-malignant [27 ITP, 12 autoimmune hemolytic anemia (AIHA), 5 sickle cell, 5 PNH, 8 SLE] and 2) malignant [13 lymphoma, 8 multiple myeloma (MM), 11 MDS, 19 MPD] hematological disorders, as well as 3) thrombotic disorders [11 DVT, 17 hypercoagulable states] and 18 healthy controls. sCD30 was measured by ELISA using platelet poor plasma from citrated blood as well as lysates of patient red blood cells following osmotic lysis with water (1:10 dilution) versus supernatant of RBC’s diluted in PBS control.
Results. In non-malignant disorders, sCD30 was significantly higher in AIHA (142.7±195.1 u/ml, p=0.006) and SLE (73.6±33.9, p=0.0000003), but not in other diseases associated with hemolysis such as sickle cell (18.7±12.3, p=0.4) and PNH (40.8±41.1, p=0.06) nor in another autoimmune disease, ITP (23.1±16.5, p=0.2) when compared to controls (19.0±6.2). In malignant disorders, all diseases tested had significantly higher sCD30 versus control: lymphoma (94.3±108.2, p=0.003), MM (47.3±28.5, p=0.0002), MDS (47.1±35.1, p=0.001), and MPD (35.3±31.6, p=0.02). In thrombotic disorders, none were significantly different from control. The surprising difference between AIHA and ITP sCD30 levels was statistically significant as well (p=0.001). In AIHA, sCD30 was similar in both active disease and remission, although sCD30 trended higher during acute hemolysis. The source of sCD30 in AIHA was first evaluated by FACS analysis of peripheral lymphocytes, which was negative. A small subset of patients had glycophorin A+, CD30+ red blood cells, but it did not correlate with sCD30 levels. However, RBC lysates from patients with AIHA contained significant levels of CD30 by ELISA in 5 of 5 patients (10.7–170.4 u/ml) with AIHA versus 0 of 4 patients with ITP (0–9.0).
Discussion. High sCD30 levels in AIHA is a novel finding, and it is of interest to find that sCD30 is not elevated in ITP, a disorder once thought to be similar in pathophysiology. The possible explanations are: 1) AIHA may reflect a highly polarized Th2 disease whereas ITP is a more Th1-mediated disorder 2) hemolyzed RBC’s in AIHA release CD30 acquired by absorption or pinocytosis or 3) CD30 is produced and stored by RBC precursors. The negative findings of sCD30 in other hemolytic diseases has yet to be explained. Further delineation of the role of CD30 in hematologic disorders will provide new light on its elusive function. The new finding of high CD30 in AIHA and intracellular CD30 in RBC’s offers a new avenue of research on CD30 in immune-mediated hemolysis.