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In 1984, Rosen and Scott1 first described cystic hypersecretory breast lesions. This entity has a spectrum of histologically distinct lesions ranging from cystic hypersecretory hyperplasia (CHH), CHH with atypia, cystic hypersecretory carcinoma (CHC) in situ, and invasive CHC. CHH’s macroscopic examination is distinct, which shows numerous cysts of varying sizes containing gelatinous material. The cyst lining epithelium, in CHH, consists of a single layer of flattened, columnar, or cuboidal epithelium without cytological atypia. Atypical CHH shows epithelial crowding, enlarged nuclei with loss of nuclear polarity, nuclear hyperchromasia, and mitoses. The in-situ carcinoma shows intermediate to high nuclear-grade lesions with micropapillary architecture.2 Most reported cases are of in-situ CHC. Invasive CHC shows solid nests of poorly differentiated cells with no secretory characteristics.3 This rare breast cancer subtype is not included in the 5th edition of the WHO breast tumor classification. The figure above shows the macro and microscopic examination of a lesion from a 58-year-old lady who presented with a lump in her right breast for six months. Imaging revealed a large solid tumor in the upper inner quadrant of the breast. A right mastectomy was performed for this patient. On gross inspection, the skin and nipple areola complex were unremarkable. The cut surface of the breast showed two different lesions. The first was a large, solid, well-demarcated whitish mass of 8.5x6.5x4.0 cm (Figure 1A). Additionally, an ill-defined lesion was identified in the adjacent breast parenchyma composed of clusters of multiple variable-sized yellowish nodules, ranging in size from few millimetres to 1.0 cm (Figure 1B). Figure 1A – gross examination from the first lesion reveals large, well-defined solid, greyish white firm tumour of 8.5x6.5x4.0 cm (scale bar= 3 cm); B – gross examination from the second lesion shows multiple variable-sized yellowish-white nodules of 1.0 mm to 10.0 mm (scale bar 1 cm); C – photomicrograph from the solid tumour shows a cellular invasive tumour arranged in solid trabecular and sheet-like architecture with marked nuclear anaplasia and focal necrosis (H&E 100X); D – photomicrograph from the second lesion shows multiple cystically dilated spaces lined by cuboidal epithelium and filled with homogeneous eosinophilic colloid-like material with few macrophages, indicating CHH (H&E, 40X); E – photomicrograph shows CHH with nuclear atypia and epithelial multilayering (H&E 400X).: The microscopic examination of the large solid mass showed a high-grade pleomorphic invasive tumor arranged in sheets and trabeculae of cells with marked nuclear pleomorphism (Figure 1C). Mitotic figures were frequent, and a focal area of necrosis was also identified. However, no microcystic or secretory changes could be identified even on examining multiple sections. Microscopic examination from the ill-defined nodular lesions showed numerous dilated cysts lined by cuboidal to columnar epithelial cells containing colloid-like eosinophilic cyst content admixed with a few foamy macrophages (Figure 1D). Occasional cysts showed nuclear atypia and epithelial multilayering (Figure 1E). However, definite in-situ carcinoma was not detected. IHC for hormone markers revealed ER and PR negative status with strong, complete membranous Her-2-neu expression in the tumor cells. Given the high-grade pleomorphic solid tumor con-existing with CHH and CHH with atypia, the invasive tumor was diagnosed as CHC. The diagnosis of CHH can be challenging on FNA and core needle biopsy specimens. Lesions like juvenile papillomatosis, fibrocystic change, columnar cell change with or without atypia, extravasation mucocele, mucinous carcinoma, secretory carcinoma, ‘clinging’ type DCIS, and metastatic thyroid carcinoma can mimic the morphology of CHH.4 Although CHH is considered a benign lesion, malignant transformation on long-term follow-up has been reported.2 Also, there is a chance of having an in-situ or high-grade invasive tumor component with CHH. Hence, a diagnosis of CHH should alert the physician about possible association with malignancy, and a wide local excision followed by thorough sampling should be performed to look for any invasive tumor.5 In conclusion, cystic hypersecretory lesions rarely encountered entities with a wide spectrum of lesions, from benign to overtly malignant. Pathologists should be well versed in the gross and microscopic features and consider the possible diagnostic pitfalls while dealing with this tumor. Although cystic hypersecretory carcinoma is not identified as a separate entity in the WHO 5th edition of breast tumor classification, associated CHH in the surrounding parenchyma indicates the invasive tumor as an invasive CHC. The available literature is limited; however, most cases of invasive CHC are high-grade solid tumors, as encountered in this case.

Intramuscularly administered vaccines stimulate robust serum neutralizing antibodies, yet they are often less competent in eliciting sustainable "sterilizing immunity" at the mucosal level. Our study uncovers a strong temporary neutralizing mucosal component of immunity, emanating from intramuscular administration of an mRNA vaccine. We show that saliva of BNT162b2 vaccinees contains temporary IgA targeting the receptor-binding domain (RBD) of severe acute respiratory syndrome coronavirus-2 spike protein and demonstrate that these IgAs mediate neutralization. RBD-targeting IgAs were found to associate with the secretory component, indicating their bona fide transcytotic origin and their polymeric multivalent nature. The mechanistic understanding of the high neutralizing activity provided by mucosal IgA, acting at the first line of defense, will advance vaccination design and surveillance principles and may point to novel treatment approaches and new routes of vaccine administration and boosting. [ABSTRACT FROM AUTHOR]

Abstract Objective Rheumatoid arthritis (RA) is often complicated with chronic lung diseases (CLD), including interstitial lung disease (ILD) and airway disease, which occur as extra-articular manifestations. CLD in RA have been associated with the production of rheumatoid factor (RF), anti-citrullinated peptide antibody (ACPA), or anti-carbamylated protein (CarP) antibody. However, few validation studies have been performed thus far. In the present study, we investigated the association of RF, ACPA, and anti-CarP antibodies with RA complicated with CLD. Methods Sera from RA patients with or without CLD were collected. The levels of serum RF, RF immunoglobulin A (IgA), ACPA IgG, ACPA IgA, and ACPA secretory component (SC) were measured using enzyme-linked immunosorbent assay. Results The comparison of RA patients with and without CLD showed that RF IgA was associated with ILD (mean ± standard deviation: 206.6 ± 400.5 vs. 95.0 ± 523.1 U/ml, respectively, P = 1.13 × 10− 8), particularly usual interstitial pneumonia (UIP) (263.5 ± 502.0 U/ml, P = 1.00 × 10− 7). ACPA SC was associated with RA complicated with ILD (mean ± standard deviation: 8.6 ± 25.1 vs. 2.3 ± 3.4 U/ml, respectively, P = 0.0003), particularly nonspecific interstitial pneumonia (NSIP) (10.7 ± 31.5 U/ml, P = 0.0017). Anti-CarP antibodies were associated with RA complicated with ILD (0.042 ± 0.285 vs. 0.003 ± 0.011 U/ml, respectively, P = 1.04X10− 11). Conclusion RF IgA and ACPA SC in RA were associated with UIP and NSIP, respectively, suggesting different specificities in patients with RA. Anti-CarP antibodies were associated with ILD in RA. These results may help elucidate the different pathogeneses of UIP and NSIP in RA.

Intramuscularly administered vaccines stimulate robust serum neutralizing antibodies, yet they are often less competent in eliciting sustainable “sterilizing immunity” at the mucosal level. Our study uncovers a strong temporary neutralizing mucosal component of immunity, emanating from intramuscular administration of an mRNA vaccine. We show that saliva of BNT162b2 vaccinees contains temporary IgA targeting the receptor-binding domain (RBD) of severe acute respiratory syndrome coronavirus-2 spike protein and demonstrate that these IgAs mediate neutralization. RBD-targeting IgAs were found to associate with the secretory component, indicating their bona fide transcytotic origin and their polymeric multivalent nature. The mechanistic understanding of the high neutralizing activity provided by mucosal IgA, acting at the first line of defense, will advance vaccination design and surveillance principles and may point to novel treatment approaches and new routes of vaccine administration and boosting.

Human milk provides immunoglobulins (Igs) that supplement the passive immune system of neonates; however, the extent of survival of these Igs during gastric digestion and whether this differs between preterm and term infants remains unknown. Human milk, and infant gastric samples at 2 h post-ingestion were collected from 15 preterm (23⁻32 week gestational age (GA)) mother-infant pairs and from 8 term (38⁻40 week of GA) mother-infant pairs within 7⁻98 days postnatal age. Samples were analyzed via ELISA for concentration of total IgA (secretory IgA (SIgA)/IgA), total secretory component (SC/SIgA/SIgM), total IgM (SIgM/IgM), and IgG as well as peptidomics. Total IgA concentration decreased by 60% from human milk to the preterm infant stomach and decreased by 48% in the term infant stomach. Total IgM and IgG concentrations decreased by 33% and 77%, respectively, from human milk to the term infant stomach but were stable in the preterm infant stomach. Release of peptides from all Ig isotypes in the term infant stomach was higher than in the preterm stomach. Overall, the stability of human milk Igs during gastric digestion is higher in preterm infant than in term infants, which could be beneficial for assisting the preterm infants' immature immune system.

As central effectors of the adaptive immune response, immunoglobulins, or antibodies, provide essential protection from pathogens through their ability to recognize foreign antigens, aid in neutralization, and facilitate elimination from the host. Mammalian immunoglobulins can be classified into five isotypes—IgA, IgD, IgE, IgG, and IgM—each with distinct roles in mediating various aspects of the immune response. Of these isotypes, IgA and IgM are the only ones capable of multimerization, arming them with unique biological functions. Increased valency of polymeric IgA and IgM provides high avidity for binding low-affinity antigens, and their ability to be transported across the mucosal epithelium into secretions by the polymeric immunoglobulin receptor allows them to play critical roles in mucosal immunity. Here we discuss the molecular assembly, structure, and function of these multimeric antibodies. [ABSTRACT FROM AUTHOR]

The polymeric Ig receptor (pIgR) transports polymeric Abs across epithelia to the mucosa, where proteolytic cleavage releases the ectodomain (secretory component [SC]) as an integral component of secretory Abs, or as an unliganded protein that can mediate interactions with bacteria. SC is conserved among vertebrates, but domain organization is variable: mammalian SC has five domains (D1-D5), whereas avian, amphibian, and reptilian SC lack the D2 domain, and fish SC lacks domains D2-D4. In this study, we used double electron-electron resonance spectroscopy and surface plasmon resonance binding studies to characterize the structure, dynamics, and ligand binding properties of avian SC, avian SC domain variants, and a human SC (hSC) variant lacking the D2 domain. These experiments demonstrated that, unlike hSC, which adopts a compact or "closed" domain arrangement, unliganded avian SC is flexible and exists in both closed and open states, suggesting that the mammalian SC D2 domain stabilizes the closed conformation observed for hSC D1-D5. Experiments also demonstrated that avian and mammalian pIgR share related, but distinct, mechanisms of ligand binding. Together, our data reveal differences in the molecular recognition mechanisms associated with evolutionary changes in the pIgR protein.

As a first-line vertebrate immune defense, the polymeric immunoglobulin receptor (pIgR) transports polymeric IgA and IgM across epithelia to mucosal secretions, where the cleaved ectodomain (secretory component; SC) becomes a component of secretory antibodies, or when unliganded, binds and excludes bacteria. Here we report the 2.6Å crystal structure of unliganded human SC (hSC) and comparisons with a 1.7Å structure of teleost fish SC (tSC), an early pIgR ancestor. The hSC structure comprises five immunoglobulin-like domains (D1-D5) arranged as a triangle, with an interface between ligand-binding domains D1 and D5. Electron paramagnetic resonance measurements confirmed the D1-D5 interface in solution and revealed that it breaks upon ligand binding. Together with binding studies of mutant and chimeric SCs, which revealed domain contributions to secretory antibody formation, these results provide detailed models for SC structure, address pIgR evolution, and demonstrate that SC uses multiple conformations to protect mammals from pathogens.

Objective: Rheumatoid arthritis (RA) is often complicated with chronic lung diseases (CLD), including interstitial lung disease (ILD) and airway disease, which occur as extra-articular manifestations. CLD in RA have been associated with the production of rheumatoid factor (RF), anti-citrullinated peptide antibody (ACPA), or anti-carbamylated protein (CarP) antibody. However, few validation studies have been performed thus far. In the present study, we investigated the association of RF, ACPA, and anti-CarP antibodies with RA complicated with CLD.Methods: Sera from RA patients with or without CLD were collected. The levels of serum RF, RF immunoglobulin A (IgA), ACPA IgG, ACPA IgA, and ACPA secretory component (SC) were measured using enzyme-linked immunosorbent assay.Results: The comparison of RA patients with and without CLD showed that RF IgA was associated with ILD (mean ± standard deviation: 206.6 ± 400.5 vs. 95.0 ± 523.1 U/ml, respectively, P = 1.13 × 10- 8), particularly usual interstitial pneumonia (UIP) (263.5 ± 502.0 U/ml, P = 1.00 × 10- 7). ACPA SC was associated with RA complicated with ILD (mean ± standard deviation: 8.6 ± 25.1 vs. 2.3 ± 3.4 U/ml, respectively, P = 0.0003), particularly nonspecific interstitial pneumonia (NSIP) (10.7 ± 31.5 U/ml, P = 0.0017). Anti-CarP antibodies were associated with RA complicated with ILD (0.042 ± 0.285 vs. 0.003 ± 0.011 U/ml, respectively, P = 1.04X10- 11).Conclusion: RF IgA and ACPA SC in RA were associated with UIP and NSIP, respectively, suggesting different specificities in patients with RA. Anti-CarP antibodies were associated with ILD in RA. These results may help elucidate the different pathogeneses of UIP and NSIP in RA. [ABSTRACT FROM AUTHOR]

Summary: Autoantibodies related to rheumatoid arthritis (RA), such as anti‐citrullinated protein antibodies (ACPA), are often detectable in the preclinical period years before arthritis onset. However, events triggering arthritis development remain incompletely known. We aimed to determine whether ACPA isotype levels are prognostic for arthritis development in patients presenting with immunoglobulin (Ig)G ACPA and musculoskeletal pain. Study participants (n = 82) had musculoskeletal pain of any sort and duration and a positive IgG ACPA test. None of the patients had arthritis upon clinical examination at baseline, but during follow‐up (mean = 6 years), 48% developed at least one arthritic joint. IgG, IgA, IgM and secretory component (SC)‐containing ACPA was measured in longitudinally collected serum samples. Cox regression analysis was performed to test the prognostic value of baseline antibody levels and changes over time. All analysed ACPA isotype levels were associated with arthritis development in univariable Cox regression analysis. In multivariable analysis, baseline SC ACPA levels were independently prognostic for arthritis development in multivariable analysis [hazard ratio (HR) = 1·006, 95% confidence interval (CI) = 1·001–1·010, P = 0·012]. There were no significant changes in ACPA isotype levels over time, and no significant association between changes over time and arthritis development. In this prospective longitudinal study, baseline serum SC ACPA levels, but neither IgG, IgA nor IgM ACPA are prognostic for future arthritis development. Repeated measurement of ACPA isotypes do not bring additional prognostic value. The results reinforce a mucosal connection in RA development and encourage further exploration of the mechanisms underlying secretory ACPA formation as a trigger for arthritis development. [ABSTRACT FROM AUTHOR]

Key message: A plant-derived secretory component conferred protease-resistance to Shiga toxin-specific mammalian immunoglobulin A. The protease-resistance was functionally demonstrated by a toxin neutralization assay. Secretory component (SC) is believed to play roles in such as the protease-resistance of secretory immunoglobulin A (SIgA), allowing it to function on mucosae. Although the use of a plant expression system for SIgA production has been increasing, it has not been sufficiently assessed as to whether heterologously expressed SC could functionally contribute to the protease-resistance of SIgA. Here, we reconstituted SIgA using plant-derived SC and tested for changes in vulnerability to protease challenge. With glutathione redox buffers, plant-derived SC and mammalian cell-derived dimeric IgA (dIgA) specific for Shiga toxin 1 (Stx1) efficiently formed SIgA. Prior ammonium sulfate precipitation of dIgA was also shown to be useful to enhance the formation of SIgA. The reconstituted SIgA was treated with two gastrointestinal proteases, pepsin and trypsin. After 2-h pepsin treatment, the signal from SIgA remained at 42% with plant-derived SC-reconstitution while that from dIgA remained at 12% without SC-reconstitution on western blot analysis. Similarly, the signal from SIgA remained at 74% with SC but that from dIgA remained at 36% without SC after 4-h trypsin treatment. Furthermore, an effect of SC-reconstitution of dIgA on pepsin-resistance was observed in a toxin neutralization assay involving Vero cells. These results indicated that the plant-derived SC could contribute to the production of orally applicable SIgA. [ABSTRACT FROM AUTHOR]

Secretory carcinoma of the breast (SBC) is a rare breast neoplasm. Most of the patients present at an early stage with a relatively indolent clinical course. Lymph node and distant metastasis are also very infrequent. The histomorphological features of the secretory breast carcinoma are quite characteristic. Predominantly three histological patterns, solid, microcystic, and tubular, have been noted with copious amounts of intra and extracellular secretory material. Most commonly, no positivity for estrogen receptor (ER), progesterone receptor (PR) and ERBB2(HER2/neu) is observed in SBCs. As SBC can occasionally be hormone receptor-positive, they should not be categorized in the triple-negative breast carcinoma (TNBC) group in general. A very characteristic genetic translocation t (12;15) has been noted in this rare tumor, resulting in a fusion between ETV6 and NTRK3 proteins. We present a case of a 60-year-old lady who presented with right breast lump of 1-month duration and was managed by lumpectomy and sentinel lymph node dissection. Axillary dissection was not performed because the sentinel lymph node biopsy was negative. Postoperative radiotherapy was given to the right breast with a boost to the tumor bed. No adjuvant chemotherapy was given No recurrence has been noted even after a year of the completion of treatment

Abstract Objective To conduct a proof-of-concept study on preferential binding of polymeric IgA (pIgA) using a novel recombinant rabbit/human chimeric secretory component (cSC) and preliminary assessment of the diagnostic potential of virus-specific pIgA in discriminating acute hepatitis A, E, and C (HAV, HEV, HCV) patients and uninfected controls using an indirect enzyme-linked immunoassay. Results cSC binds > 0.06 μg/ml of purified human and mouse pIgA with negligible cross-reactivity against IgM and IgA. Virus-specific pIgA was significantly higher in serum of acute HAV (n = 6) and HEV (n = 12) patients than uninfected samples (HEV: p

Key message: A key module, secretory component (SC), was efficiently expressed in Arabidopsis thaliana. The plant-based SC and immunoglobulin A of animal or plant origin formed secretory IgA that maintains antigen-binding activity.Abstract: Plant expression systems are suitable for scalable and cost-effective production of biologics. Secretory immunoglobulin A (SIgA) will be useful as a therapeutic antibody against mucosal pathogens. SIgA is equipped with a secretory component (SC), which assists the performance of SIgA on the mucosal surface. Here we produced SC using a plant expression system and formed SIgA with dimeric IgAs produced by mouse cells as well as by whole plants. To increase the expression level, an endoplasmic reticulum retention signal peptide, KDEL (Lys-Asp-Glu-Leu), was added to mouse SC (SC-KDEL). The SC-KDEL cDNA was inserted into a binary vector with a translational enhancer and an efficient terminator. The SC-KDEL transgenic Arabidopsis thaliana produced SC-KDEL at the level of 2.7% of total leaf proteins. In vitro reaction of the plant-derived SC-KDEL with mouse dimeric monoclonal IgAs resulted in the formation of SIgA. When reacted with Shiga toxin 1 (Stx1)-specific ones, the antigen-binding activity was maintained. When an A. thaliana plant expressing SC-KDEL was crossed with one expressing dimeric IgA specific for Stx1, the plant-based SIgA exhibited antigen-binding activity. Leaf extracts of the crossbred transgenic plants neutralized Stx1 cytotoxicity against Stx1-sensitive cells. These results suggest that transgenic plants expressing SC-KDEL will provide a versatile means of SIgA production. [ABSTRACT FROM AUTHOR]

The 17-juxtamembrane cytoplasmic residues of the polymeric immunoglobulin receptor contain an autonomous basolateral targeting signal that does not mediate rapid endocytosis (Casanova, J. E., G. Apodaca, and K. E. Mostov. Cell. 66:65-75). Alanine-scanning mutagenesis identifies three residues in this region, His656, Arg657, and Val660, that are most essential for basolateral sorting and two residues, Arg655 and Tyr668, that play a lesser role in this process. Progressive truncations suggested that Ser664 and Ile665 might also play a role in basolateral sorting. However, mutation of these residues to Ala or internal deletions of these residues did not affect basolateral sorting, indicating that these residues are probably not required for basolateral sorting. Two-dimensional NMR spectroscopy of a peptide corresponding to the 17-mer signal indicates that the sequence Arg658-Asn-Val-Asp661 has a propensity to adopt a beta-turn in solution. Residues COOH-terminal to the beta-turn (Arg662 to Arg669) seem to take up a nascent helix structure in solution. Substitution of Val660 with Ala destabilizes the turn, while mutation of Arg657 to Ala does not appear to affect the turn structure. Neither mutation detectably altered the stability of the nascent helix in the COOH-terminal portion of the peptide.

A polarized cell, to maintain distinct basolateral and apical membrane domains, must tightly regulate vesicular traffic terminating at either membrane domain. In this study we have examined the extent to which microtubules regulate such traffic in polarized cells. Using the polymeric immunoglobulin receptor expressed in polarized MDCK cells, we have examined the effects of nocodazole, a microtubule-disrupting agent, on three pathways that deliver proteins to the apical surface and two pathways that deliver proteins to the basolateral surface. The biosynthetic and transcytotic pathways to the apical surface are dramatically altered by nocodazole in that a portion of the protein traffic on each of these two pathways is misdirected to the basolateral surface. The apical recycling pathway is slowed in the presence of nocodazole but targeting is not disrupted. In contrast, the biosynthetic and recycling pathways to the basolateral surface are less affected by nocodazole and therefore appear to be more resistant to microtubule disruption.

Competing Interests: Conflict of interest: None.

The N -glycosylation of immunoglobulin (Ig) G, the major antibody in the circulation of human adults, is well known for its influence on antibody effector functions and its alterations with various diseases. In contrast, knowledge on the role of glycans attached to IgA, which is a key immune defense agent in secretions, is very scarce. In this study we aimed to characterize the glycosylation of salivary (secretory) IgA, including the IgA joining chain (JC), and secretory component (SC) and to compare IgA and IgG glycosylation between human plasma and saliva samples to gain a first insight into oral cavity-specific antibody glycosylation. Plasma and whole saliva were collected from 19 healthy volunteers within a 2-h time window. IgG and IgA were affinity-purified from the two biofluids, followed by tryptic digestion and nanoLC-ESI-QTOF-MS(/MS) analysis. Saliva-derived IgG exhibited a slightly lower galactosylation and sialylation as compared to plasma-derived IgG. Glycosylation of IgA1, IgA2, and the JC showed substantial differences between the biofluids, with salivary proteins exhibiting a higher bisection, and lower galactosylation and sialylation as compared to plasma-derived IgA and JC. Additionally, all seven N -glycosylation sites, characterized on the SC of secretory IgA in saliva, carried highly fucosylated and fully galactosylated diantennary N -glycans. This study lays the basis for future research into the functional role of salivary Ig glycosylation as well as its biomarker potential. [ABSTRACT FROM AUTHOR]