Human follicular helper T lymphocytes critical players in antibody responses

AbstractFollicular helper T (TFH) cells control antibody responses by supporting antibody affinity maturation and memory formation. Inadequate TFH function has been found in individuals with ineffective responses to vaccines, but the mechanism underlying TFH regulation in vaccination is not understood. Here, we report that lower serum levels of the metabolic hormone leptin associate with reduced vaccine responses to influenza or hepatitis B virus vaccines in healthy populations. Leptin promotes mouse and human TFH differentiation and IL-21 production via STAT3 and mTOR pathways. Leptin receptor deficiency impairs TFH generation and antibody responses in immunisation and infection. Similarly, leptin deficiency induced by fasting reduces influenza vaccination-mediated protection for the subsequent infection challenge, which is mostly rescued by leptin replacement. Our results identify leptin as a regulator of TFH cell differentiation and function and indicate low levels of leptin as a risk factor for vaccine failure.

Download Full-text

Age-stratified pediatric reference values of lymphocytes in the Moroccan population

Human Antibodies ◽

10.3233/hab-200432 ◽

2020 ◽

pp. 1-10

Author(s):

Aicha El Allam ◽

Sara El Fakihi ◽

Hicham Tahoune ◽

Karima Sahmoudi ◽

Houria Bousserhane ◽

...

Keyword(s):

T Lymphocytes ◽

Reference Values ◽

Blood Lymphocyte ◽

Healthy Subjects ◽

Lymphocyte Subsets ◽

Age Groups ◽

Lymphocyte Subpopulation ◽

Study Group ◽

Moroccan Population ◽

Helper T Lymphocytes

The number of circulating lymphocytes is altered in a number of diseases including either increase (lymphocytosis) or decrease (lymphocytopenia). Therefore, the assessment of total blood lymphocyte numbers and the relative distribution of lymphocyte subsets is a critical front-line tool in the clinical diagnosis of a number of diseases, including pediatric diseases and disorders. However, the interpretation of this data requires comparison of patient’s results to reliable reference values. Blood lymphocyte subpopulation numbers are also subject to genetic polymorphisms, immunogenic and environmental factors and vary greatly between populations. While the best practice reference values should be established within local representative populations of healthy subjects, to date, Caucasian reference values are used in Morocco due to the absence of indigenous reference values. Potential differences in blood lymphocyte subpopulation reference values between Caucasian versus Moroccan populations can adversely affect the diagnosis of pediatric and childhood diseases and disorders such as primary immunodeficiency (PID) in Morocco. OBJECTIVE: The aim of this study was to establish the age-stratified normal reference values of blood lymphocyte subsets for the pediatric Moroccan population. METHODS: We measured the concentration of lymphocyte subpopulations by flow cytometry from 83 Moroccan healthy subjects stratified into 5 age groups of 0–1, 1–2, 2–6, 6–12 and > 12–18 (adult). RESULTS: The absolute and relative amounts of the main lymphocyte subsets of T-cells, B cells and Natural Killer (NK) cells were measured and compared to previously described reference values from Cameroonian, Turkish, American and Dutch populations. Additionally, we also observed an age-related decline in the absolute population sizes of lymphocyte subsets within our study group. Relative proportions of CD3+CD4+ helper T lymphocytes decreased with increasing age and by 12 years-adult age, both proportions of CD3+CD4+ helper T lymphocytes and CD3+CD8+ cytotoxic T lymphocytes, as well as CD3-CD19+ B lymphocytes were also decreased. Finally, we compared the median values and range of our Moroccan study group with that of published results from Cameroon, Turkey, USA and Netherlands and observed significant differences in median and mean values of absolute number and relative proportions of lymphocyte subsets especially at 0–1 years and 1–2 years age groups. Above age 12 years, the Moroccan values were lower. For NK cells, the Moroccan values are also lower. CONCLUSIONS: The results of this study have a significant impact in improving the threshold values of the references intervals routinely used in the diagnosis of paediatric diseases such as PIDs or mother-to-child transmitted HIV within the Moroccan population.

Download Full-text

Influenza virus infection expands the breadth of antibody responses through IL-4 signalling in B cells

Nature Communications ◽

10.1038/s41467-021-24090-z ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Kosuke Miyauchi ◽

Yu Adachi ◽

Keisuke Tonouchi ◽

Taiki Yajima ◽

Yasuyo Harada ◽

...

Keyword(s):

B Cells ◽

Virus Infection ◽

Influenza Virus Infection ◽

Public Health Problem ◽

Influenza Viruses ◽

Antibody Responses ◽

Major Public Health Problem ◽

Follicular Helper ◽

Protective Antibodies ◽

Shared Epitopes

AbstractInfluenza viruses are a major public health problem. Vaccines are the best available countermeasure to induce effective immunity against infection with seasonal influenza viruses; however, the breadth of antibody responses in infection versus vaccination is quite different. Here, we show that nasal infection controls two sequential processes to induce neutralizing IgG antibodies recognizing the hemagglutinin (HA) of heterotypic strains. The first is viral replication in the lung, which facilitates exposure of shared epitopes that are otherwise hidden from the immune system. The second process is the germinal center (GC) response, in particular, IL-4 derived from follicular helper T cells has an essential role in the expansion of rare GC-B cells recognizing the shared epitopes. Therefore, the combination of exposure of the shared epitopes and efficient proliferation of GC-B cells is critical for generating broadly-protective antibodies. These observations provide insight into mechanisms promoting broad protection from virus infection.

Download Full-text