The Immune system - Bulwark against Disease

A T-helper cell.
© HZI/Manfred Rohde
A T-helper cell.

Each second of our lives, we are being attacked by numerous pathogens such as Viruses and bacteria. Our immune system is constantly busy fighting these invaders. Without the innate defence system of our body, which consists of various types of cells and molecules, we would be defenceless against these attacks.

The immune system makes use of two different mechanisms in its fight against pathogens: the non-specific and the specific Immune defence.

First line of defence: Non-specific immune defence

When pathogens invade the body, for example by way of a wound, the non-specific immune system reacts first. Anchored deeply in the genome, this first line of defence ensures that pathogens can be fought and disposed of within a few minutes.

When the body recognises foreign elements, it fights them by means of various defence cells and plasma proteins circulating in the bloodstream. These components, both cellular and humoral - which means present in the blood - can destroy the cell walls of the invaders or activate scavenger cells, which then "devour" the pathogens. Which cells and proteins participate specifically depends mainly on the type and site of the Infection because pathogens are very diverse. Researchers presume that 90 percent of all infections are successively controlled by the innate Immune defence.

Specific immune defence - A specific match for the pathogen 

If the pathogen successfully overcomes the first line of defence and spreads, the specific Immune defence gets involved. This system adapts individually to certain pathogens, matches them and develops a corresponding immune response. This is also called adaptive immune response. It gets involved when the foreign elements invade into the lymphatic tissue, a part of the lymphatic system, which pervades the entire body. This is where the Pathogens encounter B cells, which recognise the features of the pathogen by means of receptors. Based on these features, also called Antigens, Antibodies can be produced. By means of T-cells the B cells differentiate into more specialised Plasma cells that produce large amounts of highly specific Antibody and spread across the entire body.

The Antibodies prevent the pathogen from spreading further and limit its mobility and support the scavenger cells by "marking" the germs. These measures allow the Infection to be overcome.

Smart pathogens

However, despite this sophisticated defence mechanism, humans do still get ill. Mainly because pathogens are smart, adaptable and mutable. There are still many unanswered questions that are being addressed by researchers throughout the world.

Researchers at the HZI also investigate the interaction between Immune defence and pathogens. For these studies, the researchers develop new models that are adapted to the human immune system, and then study the mechanisms of immune response. They also look at the aging of the immune system and develop adjuvant substances to improve the efficacy of vaccines. The successes achieved in the past highlight how important it is for infection research to understand the complex mechanisms of the immune system. For this reason, immune response and immune interventions have moved into the focus of the HZI and are one of the three key topics at the centre.

Involved research groups

News on the topic

Julia Demann and Kathrin Delarosa
News

HZI Podcast: Our immune system competing against diseases

Our immune system successfully defends itself against pathogens on a daily basis - often without us realizing it. We notice other encounters with pathogens through cold symptoms, fever or a red, swollen area. Our immune system is then working at full speed. Prof. Kathrin de la Rosa wants to be one step ahead of the pathogens. Since 2024, she has headed the department “Personalized Immunotherapy” at the Centre for Individualized Infection Medicine (CiiM) - a joint institution of Hannover Medical School and the HZI. In the HZI podcast InFact, she reports on how she wants to improve individual defense mechanisms in people whose immune system cannot cope with the pathogen on its own and explains why she is copying tricks from nature.
28.10.2024
Arm with erythema due to Borrelia infection
News

Lyme disease: Probability of developing the disease is genetically predisposed

Lyme disease is the most common disease transmitted by tick bites in Germany. Whether a particular genetic predisposition plays a role in the development of the disease and which immunological processes in the body are involved is not yet sufficiently understood. A research team from the Centre for Individualised Infection Medicine (CiiM), a joint institution of the Helmholtz Centre for Infection Research (HZI) and Hannover Medical School (MHH), has now discovered a responsible gene variant and the immune parameters involved in cooperation with Radboud University Hospital (Radboundumc; Radboud Universitair Medisch Centrum) and Amsterdam UMC (both in the Netherlands). The researchers have published their findings in two studies. These have been published in the journal Nature Communications and BMC Infectious Diseases.
13.05.2024
Vero6 cells (renal epithelial cells) infected with SARS-CoV-2
News

Diversity is the key

The so-called B cells are part of the immune system's memory. Their memories of previous infections or vaccinations provide the template for antibodies that have a protective effect the next time they come into contact with a pathogen. Researchers at TWINCORE, Centre for Clinical and Experimental Infection Research, have now been able to show that the combination of infection and subsequent vaccination in the case of the SARS-CoV-2 coronavirus even protects against future variants of the virus by the memory cells virtually predicting the future. The team describes how this works in the European Journal of Immunology. The TWINCORE is a joint institution of the Helmholtz Centre for Infection Research (HZI) in Braunschweig and Hannover Medical School (MHH).
25.04.2024
3D illustration of the cytomegalovirus
News

Hijacking in the immune system

The human cytomegalovirus, HCMV for short, lies dormant unnoticed in the body of most people for their entire lives. In immunocompromised individuals, however, the virus can cause life-threatening infections. It infects dendritic cells, a specific type of cell in the immune system. Although the majority of them are infected, only a few of them immediately execute the virus's genetic programme. Researchers at TWINCORE, Centre for Experimental and Clinical Infection Research, have now been able to show which signalling pathways of the innate immune system the virus is targeting in order to have itself produced by the host cells. They have published their findings in the journal Nature Communications. The TWINCORE is a joint institution of Hannover Medical School (MHH) and the Helmholtz Centre for Infection Research (HZI) in Braunschweig.
29.02.2024
Martina Palatella (left) and Margherita Pevere in the laboratory of the department “Experimental Immunology”.
News

Margherita Pevere: Immune cells become biological art objects

It is widely known that the cells of the human immune system are natural works of art that protect us from serious diseases on a daily basis. Now they are also part of an art project at the Helmholtz Centre for Infection Research (HZI) in Braunschweig: The international artist Margherita Pevere used the HZI laboratories to examine her own immune cells and will create a work of art from the results. Pevere is supported in her work by Martina Palatella, a doctoral researcher in the HZI department “Experimental Immunology” headed by Prof Jochen Hühn.
15.02.2024
Group Picture of Participants of the ENLIGHT-TEN+ Winter School
News

Next generation scientists deepen their knowledge of translational medicine and drug production

From 13 to 17 November 2023, 28 young scientists gathered at BAYER in Berlin to take part in the Winter School for Translational Medical Research and Drug Development organized by ENLIGHT-TEN+ and EATRIS. Experts from science and industry provided in-depth insights into the basics of drug production and introduced the young scientists to the processes through interactive exercises and case studies. BAYER is a member of the ENLIGHT-TEN+ consortium and was primarily responsible for organizing the Winter School.
21.12.2023
News

Structure of a central component of the human immune system revealed

A central component of the human immune system, the NLRP3 inflammasome plays an important role in fighting off infections. However, its chronic activation is also implicated in a variety of common diseases, such as Alzheimer’s, Parkinson’s, multiple sclerosis, atherosclerosis, gout, and type II diabetes. The NLRP3 inflammasome occurs primarily in specialized immune cells in the blood and elsewhere. It is a dense complex in which several proteins interact with each other. A key protein in this complex is known by the abbreviation ASC. In non-activated immune cells, it is distributed homogeneously throughout the cell. If the NLRP3 inflammasome is activated, all of the ASC protein present in the cell aggregates in the inflammasome complex. Under an ordinary fluorescence microscope, the ASC protein, once labeled, appears as a single, bright, nearly round spot. Due to the small size and high density of this ASC speck, scientists have been unable to elucidate details of its structure inside cells. Different models were proposed in the scientific literature but a comprehensive understanding was missing.
11.12.2023
Illustration Virus
News

A virus lurking in the connective tissue

It was previously believed that herpesviruses use certain body cells to replicate and other body cells to remain dormant, that is to remain inactive for a longer period of time. This dogma is now being questioned using the example of cytomegalovirus (CMV), a herpesvirus from the beta-herpesvirus subfamily, which can be fatal in immunocompromised transplant recipients. In a new study, scientists from the “Viral Immunology” department at the Helmholtz Centre for Infection Research (HZI) in Braunschweig have discovered that certain connective tissue cells (fibroblasts) are not only used by CMV for replication, as previously assumed. Apparently, CMV can also remain latent in the fibroblasts. The prevailing picture of an either/or - either the CMV uses a certain type of body cell for proliferation, or it remains in an inactive state there - is therefore no longer tenable. A second paradigm shift suggested by the study is the regulation of the CMV latency in cells: Apparently, the virus controls the use of fibroblasts as sites of latent or active infection not only via factors present in the cell, but also via an interaction with the immune system. The results were published in the renowned journal Nature Communications.
30.05.2023
Blood samples
News

What leads to severe COVID-19?

Infection with SARS-CoV-2 leads to severe disease in some people, whereas others do not get ill or only experience mild disease. What causes these differences is not fully understood. It is already known that an overactive innate immune system is causing severe COVID-19 disease, but it is unclear how this is regulated. A team led by Prof Yang Li, Director at the Centre for Individualised Infection Medicine (CiiM) and head of department “Computational Biology for Individualised Medicine” at the Helmholtz Centre for Infection Research (HZI), has come a step closer to answering this question. The researchers addressed the question to what extent the course of disease is genetically or epigenetically regulated. The CiiM is a joint initiative by the HZI and Hannover Medical School (MHH). In addition to Li, the team included other scientists from the HZI and the RESIST cluster of excellence.
23.02.2023
Gruppenbild
News

When the skin aches

Many people suffer from neurodermatitis (atopic dermatitis) or psoriasis. These chronic inflammatory diseases, which have so far been incurable, can lead to a significant loss of quality of life due to the agonising itching and stigmatisation in severe forms. Researchers of the exzellence cluster RESIST have now gained a number of new insights with potential clinical relevance using state-of-the-art technologies such as T-cell receptor and single-cell RNA sequencing based on skin biopsies and blood samples from patients. They have published these in the journal Allergy, currently the leading publication in the field of allergology, in two articles. The main authors include Dr Bowen Zhang from the research group of Prof Yang Li, Centre for Individualised Infection Medicine (CiiM) and TWINCORE - Centre for Experimental and Clinical Infection Research, and Dr Lennart Rösner and Dr Stephan Traidl from the team of Prof Thomas Werfel, Clinic for Dermatology, Allergology and Venereology at Hanover Medical School (MHH). The CiiM and TWINCORE are joint institutions of the Helmholtz Centre for Infection Research (HZI) in Braunschweig and MHH.
13.10.2022
Vereinfachte 3D-Darstellung von Immunzellen
News

Change with age: As bats mature their immune cells differ

A team of researchers led by Anca Dorhoi at the Friedrich-Loeffler-Institut (FLI) and Emmanuel Saliba at the Helmholtz Institute for RNA-based Infection Research (HIRI), has elucidated age-dependent variations in cellular immunity in Rousettus aegyptiacus, known as the Egyptian fruit bat, a natural reservoir for filoviruses such as Marburg Virus. Using cutting-edge single-cell technologies, they mapped the bat blood with unprecedented resolution. The scientists unveiled that progression to adult age enriches for T lymphocytes and putative regulatory myeloid cells at expenses of B cells. These findings offer deeper insights into the immune system of an important wildlife reservoir species and are now published in Cell Reports.
06.09.2022
Gruppenbild
News

How pollen increases susceptibility to virus infection

Birch pollen is not only a nuisance for allergy sufferers. They can also affect the cells of the innate immune system and make them more susceptible to viral infections. This was now shown by a team of researchers at TWINCORE in Hanover, together with cooperation partners from the University of Augsburg. They published their results in the scientific journal Allergy. The TWINCORE - Centre for Experimental and Clinical Infection Research is a joint institution of the the Helmholtz Centre for Infection Research (HZI) in Braunschweig and the Hannover Medical School (MHH).
02.09.2022
Dr. Fangfang Chen im Labor
News

Cell protection, immunomodulation and virus inhibition by an endogenous substance

The endogenous molecule itaconic acid has antiviral and anti-inflammatory effects, as researchers from TWINCORE have recently shown. In cooperation with scientists from the Helmholtz Centre for Infection Research in Braunschweig and the Helmholtz Institute for Pharmaceutical Research Saarland (HIPS), they have now investigated the closely related substance citraconic acid. The result: Citraconic acid protects cells through antioxidant and anti-inflammatory properties. It also inhibits the release of flu viruses from human cells. They published these results in the journal Nature Metabolism.
07.07.2022
A black mouse is held by a person wearing blue laboratory gloves.
News

World Day for Laboratory Animals on April 24

The Helmholtz Centre for Infection Research has set itself the goal of finding new diagnostic methods, new active substances and new therapies against infectious diseases. Here you can find out why we cannot forgo animal experiments in our research.
24.04.2022
Zellen von Listeria monocytogenes
News

Infectious agent offers protection against liver cancer

Liver cancer is the third most common cause of cancer-related deaths worldwide. So far, the treatment options for two types of liver cancer, hepatocellular carcinoma (HCC) and cholangiocarcinoma (CCA), have been inadequate, while the number of new cases has been rising. A study by researchers at the Hannover Medical School (MHH) and the Helmholtz Centre for Infection Research (HZI) now offers hope. A vaccine based on a highly attenuated infectious agent called Listeria monocytogenes proved to be safe and effective protection in premalignant and malignant liver diseases in preclinical mouse models.
18.02.2022
3D-Illustration eines Monozyten
News

Antiviral and anti-inflammatory

An international research team from TWINCORE - Centre for Experimental and Clinical Infection Research, a joint facility of the Helmholtz Centre for Infection Research (HZI) in Braunschweig and the Hannover Medical School, describes the dual effect of the endogenous substance itaconic acid, which is both antiviral and anti-inflammatory. Their study, which has now appeared in the journal PLoS Pathogens, opens up perspectives for possible therapeutic applications of itaconic acid against severe courses of disease in viral infections. 
17.02.2022
Rasterelektronenmikroskopische Aufnahme einer menschlichen B-Zelle
News

Vaccination success without B cells

Immunosuppressed patients often cannot build up good protection after a vaccination because the necessary cells of the immune system function less well or are not present at all. This has been studied especially in the drug therapy of rheumatoid arthritis. Scientists from TWINCORE and the Hannover Medical School (MHH) have now published in the journal Annals of the Rheumatic Diseases the circumstances under which this group of people can nevertheless be successfully vaccinated. Based on their data, they recommend a promising strategy for the COVID-19 vaccination of rheumatism patients who are treated with the drug Rituximab. The TWINCORE-Centre for Experimental and Clinical Infection Research is a joint institution of the MHH and the Helmholtz Centre for Infection Research (HZI) in Braunschweig.
15.07.2021
Vero6-Zellen infiziert mit SARS-CoV-2
News

Helmholtz researches holistic solutions for pandemic response

How can we apply the knowledge we have gained so far to better overcome the current crisis and prevent another pandemic in future? Helmholtz aims to find answers to these questions with two new, interdisciplinary collaborative projects. In addition to the holistic approach, the focus is also on quickly implementing the results into practice.
20.05.2021
Illustration
News

How well are we protected six months after infection or vaccination?

After exposure to a virus through infection or vaccination, the body activates a number of cells and mechanisms that can provide targeted defense against the pathogen. For the global containment of the SARS-CoV-2 pandemic, the question of how long this protection lasts is an important factor. Prof Carlos Guzmán, vaccine researcher at the Helmholtz Centre for Infection Research (HZI) in Braunschweig, Germany, summarizes what is known about long-term immunity to SARS-CoV-2 and what difference it makes whether immunity is acquired through vaccination or infection.
08.04.2021
Illustration SARS-CoV-2-Viren
News

New viruses, new challenges

Newly emerging viruses, which have previously only spread in the animal kingdom, have been able to cross the species barrier and adapt to humans as new hosts. Since the end of 2019, the coronavirus SARS-CoV-2 (Severe Acute Respiratory Syndrome Coronavirus-2) has shown that nowadays such a virus can take over the whole world in a very short time.
06.04.2021