IgA Deficiency, Autoimmunity & Pregnancy: A Population-Based Matched Cohort Study

FcαRI (CD89) is upregulated on subsets of mucosal and circulating NK cells and regulates IgA-class specific signaling and functions

Immunoglobulin A (IgA) is the predominant mucosal antibody class with both anti- and pro-inflammatory roles1-3. However, the specific role of the IgA receptor cluster of differentiation (CD)89, expressed by a subset of natural killer (NK) cells, is poorly explored. We found that CD89 protein expression on circulating NK cells is infrequent in humans and rhesus macaques, but transcriptomic analysis showed ubiquitous CD89 expression, suggesting an inducible phenotype. Interestingly, CD89+ NK cells were more frequent in cord blood and mucosae, indicating a putative IgA-mediated NK cell function in the mucosae and infant immune system. CD89+ NK cells signaled through upregulated CD3 zeta chain (CD3ζ), spleen tyrosine kinase (Syk), zeta chain-associated protein kinase 70 (ZAP70), and signaling lymphocytic activation molecule family 1 (SLAMF1), but also showed high expression of inhibitory receptors such as killer cell lectin-like receptor subfamily G (KLRG1) and reduced activating NKp46 and NKp30. CD89-based activation or antibody-mediated cellular cytotoxicity with monomeric IgA1 reduced NK cell functions, while antibody-mediated cellular cytotoxicity with combinations of IgG and IgA2 was enhanced compared to IgG alone. These data suggest that functional CD89+ NK cells survey mucosal sites, but CD89 likely serves as regulatory receptor which can be further modulated depending on IgA and IgG subclass. Although the full functional niche of CD89+ NK cells remains unexplored, these intriguing data suggest the CD89 axis could represent a novel immunotherapeutic target in the mucosae or early life.

Pregnancy in primary immunodeficiency diseases: The PREPI study

BACKGROUND

Primary immunodeficiencies (PID) are a heterogeneous group of rare inborn immunity defects. As management has greatly improved, morbidity and mortality are reduced in this population, while our knowledge on pregnancy's unfolding and outcome remains scarce.

OBJECTIVE

We conducted a retrospective monocentric study to study pregnancy outcomes in women with PID.

METHODS

The study cohort consisted of women over 18 included in the national registry for PID (CEREDIH), living in the greater Paris area, reporting ≥1 pregnancy. Data were collected through a standardized questionnaire and medical records. We analyzed PID features, pregnancy course and outcome, and neonatal features (NCT04581460).

RESULTS

We studied 93 women with PID (27 combined immunodeficiencies, 51 predominantly antibody deficiencies, and 15 innate immunodeficiencies) and their 222 pregnancies (67, 119, and 36 in each group, respectively). One hundred fifty-four (69%) of 222 pregnancies led to 157 live births, including 4 severe preterm births (3%), in the range of pregnancy outcome in the French general population. In a multivariate model, poor obstetrical outcome (fetal loss or pregnancy termination) was associated with history of severe infection (adjusted odds ratio 0.28, 95% confidence interval 0.11-0.67, P = .005). Only 59% pregnancies were led with optimal anti-infective prophylaxis; severe infections were reported in only 2 pregnancies (1%). One infant died during the neonatal period.

CONCLUSION

Pregnancy is achievable in women with a wide group of PID. Prematurity is increased and history of severe infection is associated with significant increase of fetal loss/pregnancy termination. Adjustment of care during pregnancy needs to be better delivered.

[Selective IgA deficiency]

Selective IgA deficiency (SIgAD) is defined by the European Society for Immunodeficiencies (ESID) as a serum IgA of less than 0.07g/L in patients greater than 4 years old with normal levels of IgG and IgM, normal vaccine responses, and with the exclusion of secondary causes of hypogammaglobulinemia. When serum IgA level is higher than 0.07g/L but two standard deviations below normal for age, the condition may be referred to as partial IgA deficiency, which is quite common. SIgAD is the most common primary immunodeficiency in Europe (1/600 in France) and most patients with SIgAD are asymptomatic (75-90%). The clinical complications associated with SIgAD include recurrent respiratory infections (in particular involving Haemophilus influenza and Streptococcus pneumoniae) and gastrointestinal (mainly due to Giardialamblia), autoimmune and allergic manifestations (anaphylaxis if blood products with IgA are administrated), inflammatory gastrointestinal disease. There is no specific treatment for SIgAD and each patient must be managed individually. While asymptomatic subjects do not need any treatment, it is still necessary for them to be up-to-date with vaccinations. If the patient experiences recurrent infections, prophylactic antibiotics may be beneficial. Immunoglobulin replacement therapy should be considered in patients with SIgAD and concomitant IgG subclass deficiency. Treatment for autoimmune and allergic manifestations is based on current standards of care for specific disease entities. To improve quality of life and reduce morbidity, an interdisciplinary team approach is essential.