Both the complement system and collectins play important roles in our innate immune system. The collectins, which are characterized by their inclusion of a collagen-like region and a calcium-dependent carbohydrate recognition domain, are pattern recognition molecules and include the well characterized proteins mannan-binding lectin (MBL) and the surfactant proteins SP-A/-D. Collectin liver 1 (CL-L1), collectin kidney 1 (CL-K1) and collectin placenta 1 (CL-P1) are the most recently discovered collectins. Although their function is still under investigation, accumulating information suggests that CL-L1, CL-K1 and CL-P1 play important roles in host defense by recognizing a variety of microorganisms and interacting with effector proteins, including complement components. The recent establishment of the existence of CL-K1 in the circulation in form of heteromeric complexes with CL-L1 (known as CL-LK) and its activation of the lectin pathway via MASPs, drew new attention in the complement biology, which was further strengthened by the observed interactions between CL-P1 and CRP-C1q-factor H or properdin. Deficiency of either CL-K1 or MASP-3 has been demonstrated in 3MC syndrome patients with developmental abnormalities, showing that lectin pathway components, regulation and/or activation are essential during the embryonic development; another feature that they most likely share CL-P1. Herein, we discuss the recent characteristics and roles of the collectins CL-L1, CL-K1 and CL-P1 in the complement system, in innate immunity and their possible association with disease development and pathogenesis.

Background: Collectins are considered to play a role in host defense via complement activation and

Background and objectives The COVID-19 pandemic has negatively impacted health systems worldwide, including in Bangladesh, limiting access to family planning information (FP) and services. Unfortunately, the evidence on the factors linked to such disruption is limited, and no study has addressed the link among Bangladeshis. This study aimed to examine the socioeconomic, demographic, and other critical factors linked to the use of FP in the studied areas during the COVID-19 pandemic. Methods The characteristics of the respondents were assessed using a cross-sectional questionnaire survey and descriptive statistics. The variables that were substantially linked with FP usage were identified using a Chi-square test. In addition, a multivariate logistic regression model was used to identify the parameters linked to FP in the study areas during the COVID-19 pandemic. Results The prevalence of FP use among currently married 15–49 years aged women was 36.03% suggesting a 23% (approximately) decrease compared to before pandemic data. Results also showed that 24.42% of the respondents were using oral contraceptive pills (OCP) which is lower than before pandemic data (61.7%). Multivariate regression analysis provided broader insight into the factors affecting FP use. Results showed that woman’s age, education level of the respondents, working status of the household head, locality, reading a newspaper, FP workers’ advice, currently using OCP, ever used OCP, husbands’ supportive attitude towards OCP use, duration of the marriage, ever pregnant, the number of children and dead child were significantly associated with FP use in the study areas during COVID-19 pandemic. Conclusions This study discusses unobserved factors that contributed to a reduction in FP use and identifies impediments to FP use in Bangladesh during the COVID-19 epidemic. This research further adds to our understanding of FP usage by revealing the scope of the COVID-19 pandemic’s impact on FP use in Bangladesh’s rural and urban areas.

OBJECTIVES: Although maternal tetanus immunization has been shown to be highly effective in the prevention of neonatal tetanus, unresolved questions remain concerning the required minimum number of doses and the resulting duration of effective immunity. This study examined the duration of effective immunity against neonatal tetanus provided by maternal tetanus immunization. METHODS: A randomized, double-blind cholera vaccine trial of 41,571 children and nonpregnant adult women carried out in 1974 in the Matlab comparison area of rural Bangladesh provided a unique opportunity to address dose and immunity issues. RESULTS: Children of women who received either 1 or 2 injections of tetanus toxoid experienced 4- to 14-day mortality levels consistently lower than those of children of unimmunized mothers. Analysis of neonatal-tetanus-related mortality showed that 2 injections of tetanus toxoid provided significant protection for subsequent durations of up to 12 or 13 years. CONCLUSIONS: The data demonstrate that a limited-dose regimen of maternal tetanus toxoid provides significant and extended protection against the risk of neonatal tetanus death.

Collectins are C-type lectins that are involved in innate immunity as pattern recognition molecules. Recently, collectin kidney 1 (CL-K1) has been discovered, and in vitro studies have shown that CL-K1 binds to microbes and activates the lectin complement pathway. However, in vivo functions of CL-K1 against microbes have not been elucidated. To investigate the biological functions of CL-K1, we generated CL-K1 knockout (CL-K1^-/-) mice and then performed a Streptococcus pneumoniae infection analysis. First, we found that recombinant human CL-K1 bound to S. pneumoniae in a calcium-dependent manner, and induced complement activation. CL-K1^-/- mice sera formed less C3 deposition on S. pneumoniae. Furthermore, immunofluorescence analysis in the wild-type (WT) mice demonstrated that CL-K1 and C3 were localized on S. pneumoniae in infected lungs. CL-K1^-/- mice revealed decreased phagocytosis of S. pneumoniae. Consequently, less S. pneumoniae clearance was observed in their lungs. CL-K1^-/- mice showed severe pulmonary inflammation and weight loss in comparison with WT mice. Finally, the decreased clearance and severe pulmonary inflammation caused by S. pneumoniae infection might cause higher CL-K1^-/- mice lethality. Our results suggest that CL-K1 might play an important role in host protection against S. pneumoniae infection through the activation of the lectin complement pathway.