Splenectomy outcomes in immune cytopenias: Treatment outcomes and determinants of response

BACKGROUND

Splenectomy is commonly used to treat refractory immune-mediated cytopenia, but there are no established factors that are associated with response to the procedure.

OBJECTIVES

A cohort study was conducted to evaluate the hematologic and surgical outcomes of splenectomy in adult patients with immune cytopenias and identify preoperative factors associated with response.

METHODS

Data from the Cleveland Clinic Foundation for 1824 patients aged over 18 who underwent splenectomy from 2002 to 2020 were analyzed.

RESULTS

The study found that the most common indications for splenectomy were immune thrombocytopenic purpura (ITP) and autoimmune hemolytic anemia, with a median age of 55 years and median time from diagnosis to splenectomy of 11 months. Hematologic response rates were 74% overall, with relapse in 12% of cases. Postsplenectomy discordant diagnoses were present in 13% of patients, associated with higher relapse rates. Surgery-related complications occurred in 12% of cases, whereas only 3% of patients died from disease complications. On univariate analysis, preoperative factors associated with splenectomy treatment failure were ≥3 lines of pharmacologic treatment, whereas isolated thrombocytopenia, primary ITP, and age ≤40 years had a strong association with response. The multivariable regression confirmed that treatment failure with multiple lines of medical therapy was associated with the failure to respond to splenectomy.

CONCLUSION

Overall, the study demonstrates that splenectomy is an effective treatment option for immune-mediated cytopenias with a low complication rate.

Measurement of Typhi Vi antibodies can be used to assess adaptive immunity in patients with immunodeficiency

Vaccine‐specific antibody responses are essential in the diagnosis of antibody deficiencies. Responses to Pneumovax II are used to assess the response to polysaccharide antigens, but interpretation may be complicated. Typhim Vi^®, a polysaccharide vaccine for Salmonella typhoid fever, may be an additional option for assessing humoral responses in patients suspected of having an immunodeficiency. Here we report a UK multi‐centre study describing the analytical and clinical performance of a Typhi Vi immunoglobulin (Ig)G enzyme‐linked immunosorbent assay (ELISA) calibrated to an affinity‐purified Typhi Vi IgG preparation. Intra‐ and interassay imprecision was low and the assay was linear, between 7·4 and 574 U/ml (slope = 0·99–1·00; R² > 0·99); 71% of blood donors had undetectable Typhi Vi IgG antibody concentrations. Of those with antibody concentrations  > 7·4 U/ml, the concentration range was 7·7–167 U/ml. In antibody‐deficient patients receiving antibody replacement therapy the median Typhi Vi IgG antibody concentrations were  < 25 U/ml. In vaccinated normal healthy volunteers, the median concentration post‐vaccination was 107 U/ml (range 31–542 U/ml). Eight of eight patients (100%) had post‐vaccination concentration increases of at least threefold and six of eight (75%) of at least 10‐fold. In an antibody‐deficient population (n = 23), only 30% had post‐vaccination concentration increases of at least threefold and 10% of at least 10‐fold. The antibody responses to Pneumovax II and Typhim Vi^® correlated. We conclude that IgG responses to Typhim Vi^® vaccination can be measured using the VaccZyme Salmonella typhi Vi IgG ELISA, and that measurement of these antibodies maybe a useful additional test to accompany Pneumovax II responses for the assessment of antibody deficiencies.

Netrin stimulates tyrosine phosphorylation of the UNC-5 family of netrin receptors and induces Shp2 binding to the RCM cytodomain

Caenorhabditis elegans UNC-5 and its mammalian homologues such as RCM are receptors for the secreted axon guidance cue UNC-6/netrin and are required to mediate the repulsive effects of UNC-6/netrin on growth cones. We find that C. elegans UNC-5 and mouse RCM are phosphorylated on tyrosine in vivo. C. elegans UNC-5 tyrosine phosphorylation is reduced in unc-6 null mutants, and RCM tyrosine phosphorylation is induced by netrin-1 in transfected HEK-293 cells, demonstrating that phosphorylation of UNC-5 proteins is enhanced by UNC-6/netrin stimulation in both worms and mammalian cells. An activated Src tyrosine kinase induces phosphorylation of RCM at multiple cytoplasmic tyrosine residues creating potential binding sites for cytoplasmic signaling proteins. Indeed, the NH2-terminal SH2 domain of the Shp2 tyrosine phosphatase bound specifically to a Tyr(568) RCM phosphopeptide. Furthermore, Shp2 associated with RCM in a netrin-dependent manner in transfected cells, and co-immunoprecipitated with RCM from an embryonic mouse brain lysate. A Y568F mutant RCM receptor failed to bind Shp2 and was more highly phosphorylated on tyrosine than the wild type receptor. These results suggest that netrin-stimulated phosphorylation of RCM Tyr(568) recruits Shp2 to the cell membrane where it can potentially modify RCM phosphorylation and function.

UNC-73 activates the Rac GTPase and is required for cell and growth cone migrations in C. elegans

unc-73 is required for cell migrations and axon guidance in C. elegans and encodes overlapping isoforms of 283 and 189 kDa that are closely related to the vertebrate Trio and Kalirin proteins, respectively. UNC-73A contains, in order, eight spectrin-like repeats, a Dbl/Pleckstrin homology (DH/PH) element, an SH3-like domain, a second DH/PH element, an immunoglobulin domain, and a fibronectin type III domain. UNC-73B terminates just downstream of the SH3-like domain. The first DH/PH element specifically activates the Rac GTPase in vitro and stimulates actin polymerization when expressed in Rat2 cells. Both functions are eliminated by introducing the S1216F mutation of unc-73(rh40) into this DH domain. Our results suggest that UNC-73 acts cell autonomously in a protein complex to regulate actin dynamics during cell and growth cone migrations.

Suppressors of the unc-73 gene of Caenorhabditis elegans

The unc-73 gene of Caenorhabditis elegans is necessary for proper axon guidance. Animals mutant in this gene are severely uncoordinated and also exhibit defects in cell migration and cell lineages. We have isolated coordinated revertants of unc-73 (e936). These fall into three classes: intragenic revertants, extragenic dominant suppressors (sup-39), and a single apparently intragenic mutation that is a dominant suppressor with a linked recessive lethal phenotype. sup-39 mutations cause early embryonic lethality, but escapers have a wild-type movement phenotype as larvae and adults. Gonads of sup-39 mutant animals show a novel defect: normal gonads have a single row of oocytes, but sup-39 gonads often have two rows of oocytes. This result suggests that the mutant gonad is defective in choosing on its surface only a single site form which nuclei will emerge to form oocytes. These results are interpreted in terms of an effect of unc-73 on determination of cell polarity.