Tandem substitutions in somatic hypermutation

Upon antigen recognition, activation-induced cytosine deaminase initiates affinity maturation of the B-cell receptor by somatic hypermutation (SHM) through error-prone DNA repair pathways. SHM typically creates single nucleotide substitutions, but tandem substitutions may also occur. We investigated incidence and sequence context of tandem substitutions by massive parallel sequencing of V(D)J repertoires in healthy human donors. Mutation patterns were congruent with SHM-derived single nucleotide mutations, delineating initiation of the tandem substitution by AID. Tandem substitutions comprised 5,7% of AID-induced mutations. The majority of tandem substitutions represents single nucleotide juxtalocations of directly adjacent sequences. These observations were confirmed in an independent cohort of healthy donors. We propose a model where tandem substitutions are predominantly generated by translesion synthesis across an apyramidinic site that is typically created by UNG. During replication, apyrimidinic sites transiently adapt an extruded configuration, causing skipping of the extruded base. Consequent strand decontraction leads to the juxtalocation, after which exonucleases repair the apyramidinic site and any directly adjacent mismatched base pairs. The mismatch repair pathway appears to account for the remainder of tandem substitutions. Tandem substitutions may enhance affinity maturation and expedite the adaptive immune response by overcoming amino acid codon degeneracies or mutating two adjacent amino acid residues simultaneously.Transplantation and immunomodulatio

Tandem substitutions in somatic hypermutation

Upon antigen recognition, activation-induced cytosine deaminase initiates affinity maturation of the B-cell receptor by somatic hypermutation (SHM) through error-prone DNA repair pathways. SHM typically creates single nucleotide substitutions, but tandem substitutions may also occur. We investigated incidence and sequence context of tandem substitutions by massive parallel sequencing of V(D)J repertoires in healthy human donors. Mutation patterns were congruent with SHM-derived single nucleotide mutations, delineating initiation of the tandem substitution by AID. Tandem substitutions comprised 5,7% of AID-induced mutations. The majority of tandem substitutions represents single nucleotide juxtalocations of directly adjacent sequences. These observations were confirmed in an independent cohort of healthy donors. We propose a model where tandem substitutions are predominantly generated by translesion synthesis across an apyramidinic site that is typically created by UNG. During replication, apyrimidinic sites transiently adapt an extruded configuration, causing skipping of the extruded base. Consequent strand decontraction leads to the juxtalocation, after which exonucleases repair the apyramidinic site and any directly adjacent mismatched base pairs. The mismatch repair pathway appears to account for the remainder of tandem substitutions. Tandem substitutions may enhance affinity maturation and expedite the adaptive immune response by overcoming amino acid codon degeneracies or mutating two adjacent amino acid residues simultaneously

Dictating Phenotype, Function, and Fate of Human T Cells with Co-Stimulatory Antibodies Presented by Filamentous Immune Cell Mimics

T cells require a co-stimulatory signal in addition to T-cell receptor (TCR) stimulation to achieve full activation. While most studies focus on the co-stimulatory receptor CD28, little is known about the role of the other co-stimulatory receptors in T-cell signaling. A deeper understanding of how co-stimulatory receptor signaling cooperates with TCR signaling could improve the ability to control T-cell function and benefit the design of T-cell based immunotherapies. Artificial antigen presenting cells (aAPCs) enable tight control over the signals given to T cells. In this study, filamentous polyisocyanopeptide (PIC) polymers (immunofilaments) are used as nanosized aAPCs to study the role of the engagement of six distinct co-stimulatory molecules on human T-cell phenotype, function, and fate in the context of TCR signaling. The immunofilaments highlight important roles for CD28 and CD2 signaling in T-cell priming, proliferation, cytokine production, and multifunctionality. Taken together, this work provides insight into the role of combined TCR and co-stimulation on T-cell phenotype, function, and fate using immunofilaments. Notably, the findings on the roles of co-stimulatory molecule function can be used for the rational design of future cancer immunotherapies

Donor nephrectomy: Less fatigue and better quality of life following laparascopic kidney removal compared with an open procedure by mini-incision:Blind randomised study

Objective. Determining possible differences in living donor nephrectomy procedures: laparoscopy against mini-incision concerning discomfort to the donor and the maintenance of good graft function. Design. Blind randomized study. Method. In two university medical centres, one hundred living kidney donors were randomly assigned to either total laparoscopic donor nephrectomy or mini-incision muscle-splitting open donor nephrectomy. Primary outcome was physical fatigue measured with the 'Multidimensional Fatigue Inventory' (MFI-20) during one-year follow-up. Secondary outcomes were physical function measured with the 'Short form-36' questionnaire, postoperative hospital stay, amount of pain, operating times and graft and patient survival. Results. Donors who underwent laparoscopy experienced less fatigue (difference: -1.3; 95% CI: -2.4-0.1) and physical function was better (difference: 6.2; 95% CI: 2.0-10.3) during one-year follow-up. Those donors who underwent laparoscopy required less morphine (16 mg versus 25 mg; p = 0.005) and the duration of hospital stay was shorter (3 versus 4 days; p = 0.003). The laparoscopic procedure resulted in a longer operation time (221 versus 164 min; p &lt; 0.001), a longer first warm ischaemia time (6 versus 3 min; p &lt; 0.001), and less blood loss (100 versus 240 ml; p &lt; 0.001). Recipient renal function and one-year graft survival rates did not differ. The number of preoperative and postoperative complications did not differ significantly between both surgery techniques. Conversions did not occur. Conclusion. Donor nephrectomy through laparoscopy led to less fatigue and a better quality of life compared with the open procedure. The safety factors for donors and recipients were comparable for both techniques. Laparoscopic donor nephrectomy is therefore the better surgical choice for kidney donor programmes with living donors.</p

Donor nephrectomy: Less fatigue and better quality of life following laparascopic kidney removal compared with an open procedure by mini-incision:Blind randomised study

Objective. Determining possible differences in living donor nephrectomy procedures: laparoscopy against mini-incision concerning discomfort to the donor and the maintenance of good graft function. Design. Blind randomized study. Method. In two university medical centres, one hundred living kidney donors were randomly assigned to either total laparoscopic donor nephrectomy or mini-incision muscle-splitting open donor nephrectomy. Primary outcome was physical fatigue measured with the 'Multidimensional Fatigue Inventory' (MFI-20) during one-year follow-up. Secondary outcomes were physical function measured with the 'Short form-36' questionnaire, postoperative hospital stay, amount of pain, operating times and graft and patient survival. Results. Donors who underwent laparoscopy experienced less fatigue (difference: -1.3; 95% CI: -2.4-0.1) and physical function was better (difference: 6.2; 95% CI: 2.0-10.3) during one-year follow-up. Those donors who underwent laparoscopy required less morphine (16 mg versus 25 mg; p = 0.005) and the duration of hospital stay was shorter (3 versus 4 days; p = 0.003). The laparoscopic procedure resulted in a longer operation time (221 versus 164 min; p &lt; 0.001), a longer first warm ischaemia time (6 versus 3 min; p &lt; 0.001), and less blood loss (100 versus 240 ml; p &lt; 0.001). Recipient renal function and one-year graft survival rates did not differ. The number of preoperative and postoperative complications did not differ significantly between both surgery techniques. Conversions did not occur. Conclusion. Donor nephrectomy through laparoscopy led to less fatigue and a better quality of life compared with the open procedure. The safety factors for donors and recipients were comparable for both techniques. Laparoscopic donor nephrectomy is therefore the better surgical choice for kidney donor programmes with living donors.</p