Increased circulating soluble CD40 ligand (sCD40L) is commonly associated with inflammatory disorders. We aimed to investigate whether gene polymorphisms in CD40LG, CD40 and ITGA2 are associated with a propensity to secrete sCD40L; thus, we examined this issue at the level of human platelets, the principal source of sCD40L. We performed single polymorphism and haplotype analyses to test for the effect of twelve polymorphisms across the CD40LG , CD40 and ITGA2 genes in blood donors. ITGA2 presented a positive association with rs1126643, with a significant modification in sCD40L secretion (carriers of C allele, P = 0.02), unlike the investigated CD40LG and CD40 polymorphisms. One CD40LG haplotype (TGGC) showing rs975379 (C/T), rs3092952 (A/G), rs3092933 (A/G) and rs3092929 (A/C) was associated with increased sCD40L levels (1.906 μg/L (95% CI: 1.060 to 2.751); P = 0.000009). The sCD40L level was associated with the inter-chromosomal CD40LG/CD40/ ITGA2 haplotype (ATC), displaying rs3092952 (A/G), rs1883832 (C/T) and rs1126643 (C/T), with increased sCD40L levels (P = 0.0135). Our results help to decipher the genetic role of CD40LG , CD40 and ITGA2 with regard to sCD40L levels found in platelet components. Given the crucial role of sCD40L, this haplotype study in a transfusion model may be helpful to further determine the role of haplotypes in inflammatory clinical settings.

BACKGROUND:Leucoreduction of blood components, including platelet components, is strongly encouraged but not yet universal, especially outside high income countries. As both leucocytes and platelets secrete copious amounts of pro-inflammatory cytokines/chemokines under various conditions and during storage, we investigated the potential of the respective secretory programmes of these cells in order to evaluate their subsequent pathophysiological effects.MATERIAL AND METHODS:A total of 158 individual non-leucoreduced platelet components were obtained from Tunisian donors and tested for characteristic biological response modifiers (BRM) of leukocytes (IL-1β, IL-8), platelets (sCD62P, sCD40L) and both cell types (TNF-α, RANTES) in the presence or absence of thrombin stimulation and after different periods of storage (up to 5 days). BRM levels were determined using enzyme-linked immunosorbent assays and Luminex technology. Platelet-leucocyte aggregate formation during storage was analysed using flow cytometry.RESULTS:Leucocyte- and platelet-associated BRM had clearly distinct profiles both at the onset (day 0) and termination (day 5) of the observation period but altered during the intermediate period so that their respective importance was inverted; in fact, the profiles were merged and indistinguishable on days 2-3. The leucocyte-derived BRM largely dominated over platelet-derived ones and further altered the BRM platelet secretion programme.DISCUSSION:This study contributes substantial, new information on leucocyte/platelet interactions and their likely role in transfusion when leucodepletion cannot be performed or is only partially achieved.

The concept of the immunogenicity of an antigen is frequently encountered in the context of vaccine development, an area of intense interest currently due to the emergence or re-emergence of infectious pathogens with the potential for worldwide spread. However, the theoretical notion of immunogenicity as discussed in older textbooks of immunology needs reconsideration due to advances in our understanding of immunologic responses. Immunogenicity is a property that can either be a desirable attribute, for example in the generation of an effective protective immunity against infectious pathogens or an undesirable trait, for example when it relates to novel therapeutic compounds and drugs, where an immune response needs to be prevented or inhibited. In this Forum Article, we aimed to revisit the issue of immunogenicity to discuss a series of simple questions relevant to the concept that are frequently rephrased but incompletely resolved in the immunologic literature.

Les concentrés plaquettaires (CP) sont des produits sanguins labiles essentiels dans le traitement de la thrombocytopénie. Malgré une préparation rigoureuse, ils provoquent encore des effets indésirables receveurs (EIR), parfois graves. Des molécules proinflammatoires, et notamment les cytokines/chimiokines (biologic response modifiers [BRM]), qui seraient secrétées par les plaquettes pendant le stockage, sont suspectées d’en être responsables. Nous avons exploré la concentration de 6 BRM (IL-1β, TNFα, RANTES, sCD40L, IL-8 et sCD62p) dans 152 CP non déleucocytés collectés au CRTS de Sousse, Tunisie, et leur évolution durant le stockage. Nous avons aussi étudié, à différents temps, la réponse plaquettaire à un analogue de la thrombine, le TRAP. Enfin, nous avons évalué l’influence de certains polymorphismes régulateurs de ces BRM dans leur sécrétion au cours du stockage. L’évolution de la concentration des BRM dans les CP montre une augmentation de l’ensemble des 6 BRM durant le stockage. Toutefois, sCD40L et RANTES atteignent un plateau à partir de j3. Par ailleurs, la réponse au TRAP était très forte lors des prélèvements au moment de la préparation (j0), pour chuter fortement au bout de 24 h et remonter progressivement par la suite, jusqu’à j5. Enfin, 2 polymorphismes ont été associés à une hyperproduction de BRM dans les CP : rs6127 de CD62p (allèle G) et rs1143627 IL1β (allèle C) Ces données pourraient être utiles dans les processus de qualification afin de sélectionner des donneurs porteurs de polymorphismes à faibles risques pour des receveurs ayant des antécédents d’EIR, au regard des BRM.

The CD40 ligand (CD40L) is a transmembrane molecule of crucial interest in cell signaling in innate and adaptive immunity. It is expressed by a variety of cells, but mainly by activated T-lymphocytes and platelets. CD40L may be cleaved into a soluble form (sCD40L) that has a cytokine-like activity. Both forms bind to several receptors, including CD40. This interaction is necessary for the antigen specific immune response. Furthermore, CD40L and sCD40L are involved in inflammation and a panoply of immune related and vascular pathologies. Soluble CD40L is primarily produced by platelets after activation, degranulation and cleavage, which may present a problem for transfusion. Soluble CD40L is involved in adverse transfusion events including transfusion related acute lung injury (TRALI). Although platelet storage designed for transfusion occurs in sterile conditions, platelets are activated and release sCD40L without known agonists. Recently, proteomic studies identified signaling pathways activated in platelet concentrates. Soluble CD40L is a good candidate for platelet activation in an auto-amplification loop. In this review, we describe the immunomodulatory role of CD40L in physiological and pathological conditions. We will focus on the main signaling pathways activated by CD40L after binding to its different receptors.

Alloimmunization is an undesirable iatrogenic effect of transfusion and transplantation. In fact, recipients can be considered as responders or not responders, in a continuum from tolerance, including organ transplantation and transfusion, to polyimmunized and refractory patients. New models and large studies have enabled a better understanding of the mechanisms that induce specific alloantibody (alloAb) generation. Here, we focus on risk factors of alloimmunization. We review the alloantibody characteristics, summarize the different leukocytes involved in their induction, and suggest some hypotheses.

The CD40 ligand (CD40L/CD154), a member of TNF superfamily, is notably expressed on activated CD4+ T-cells and stimulated platelets. CD40L is linked to a variety of pathologies and to acute transfusion reactions (ATR). Mutations in this gene (CD40LG) lead to X-linked hyper-IgM syndrome. Some CD40LG polymorphisms are associated with variable protein expression. The rationale behind this study is that CD40L protein has been observed to be involved in ATR. We wondered whether genetic polymorphisms are implicated. We investigated genetic diversity in the CD40LG using DHPLC and capillary electrophoresis for screening and genotyping (n = 485 French and Tunisian blood donors). We identified significant difference in the CD40LG linkage pattern between the two populations. Variant minor alleles were significantly over-represented in Tunisian donors (P<0.0001 to 0.0270). We found higher heterogeneity in the Tunisian, including three novel low frequency variants. As there was not a particular pattern of CD40LG in single apheresis donors whose platelet components induced an ATR, we discuss how this information may be useful for future disease association studies on CD40LG.