Immunology: Defense Against Infection

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What is the principal role of the Th2 response in acquired immunity?

Secretion of IFN-γ

Destruction of infected cells

Activation of macrophages

Production of antibodies (correct)

Which immune cells are primarily responsible for eliminating intracellular bacteria?

CD8 cytotoxic T cells (correct)

Neutral killer cells

Helper T cells

B cells

In the context of tuberculosis, which type of immune response is activated for effective elimination of the bacteria?

Th1 response (correct)

Th2 response

Humoral immunity

Innate immunity

What outcome does a Th2-dominated response have in leprosy infections?

Severe tissue destruction Signup and view all the answers

What is the role of natural killer (NK) cells in innate immunity?

Killing infected cells Signup and view all the answers

Which bacteria are notably resistant to phagocytosis and cause chronic infections?

Mycobacterium leprae Signup and view all the answers

What is the impact of the interaction between Th1 and Th2 responses in immune system functioning?

They determine the severity of certain diseases Signup and view all the answers

The inflammatory response is a primary component of which type of immunity?

Innate immunity Signup and view all the answers

What are the four fundamental kinds of microbial infectious agents that microbiologists study?

Bacteria, Fungi, Viruses, and Parasites Signup and view all the answers

What factors determine the outcome of host-parasite interactions?

Characteristics of both the host and the microbe Signup and view all the answers

Which two conditions result in adverse immune response according to the balance theory mentioned?

Under-reaction and excessive response Signup and view all the answers

Which immune response is primarily activated against viruses?

Anti-viral immune response Signup and view all the answers

What is NOT a characteristic that defines the phenotype of acute infectious disease?

Duration of symptoms Signup and view all the answers

Which of the following is most closely associated with parasitic infections?

Protozoa Signup and view all the answers

What is a key aspect of immune evasion by pathogens?

Pathogens can hide from immune detection Signup and view all the answers

Which type of immune response would be engaged against an extracellular bacterium?

Humoral immune response Signup and view all the answers

What role do antibodies play in humoral immunity against viruses?

They neutralize viruses and prevent attachment to target cells. Signup and view all the answers

Which cell type is primarily responsible for killing virus-infected cells through direct recognition of viral antigens?

Cytotoxic T-cells (CTLs) Signup and view all the answers

How do interferons (IFNs) inhibit viral replication in infected cells?

By inhibiting intracellular replication of viruses. Signup and view all the answers

What is the purpose of the Cytokines released by T-helper cells during a viral infection?

To attract and activate macrophages. Signup and view all the answers

What mechanism describes Antibody-Dependent Cell-mediated Cytotoxicity (ADCC)?

Antibodies bind to virus-infected cells which are then lysed by immune cells. Signup and view all the answers

Which of the following best describes the action of interferons in the context of viral infections?

They act early in viral diseases before antibodies are produced. Signup and view all the answers

What function do Mx proteins have in the innate immune response to viruses?

They block the transport of viral nucleoproteins into the nucleus. Signup and view all the answers

Which type of immunity is primarily mediated by Natural Killer (NK) cells during the early stages of a viral infection?

Cell-mediated immunity Signup and view all the answers

Which mechanism allows adenoviruses to successfully evade PKR activation?

Production of VA RNA that binds PKR without activating it Signup and view all the answers

What is one of the roles of E1A produced by adenoviruses in immune evasion?

Sequesters p300/CPB co-factors to block interferon expression Signup and view all the answers

Which type of immune response is primarily responsible for combating intracellular infections?

Cell-mediated response involving effector T lymphocytes Signup and view all the answers

What determines the predominant immune response to an infection?

The cytokine signals at initial antigen contact Signup and view all the answers

What defines immunological memory?

Recovery from infection that promotes long-term immunity to re-infection Signup and view all the answers

Which cytokines are primarily associated with Th2-type immune responses?

IL-4, IL-5, IL-10, and IL-13 Signup and view all the answers

What is a common response to helminth infections in the host immune response?

Strong production of immunoglobulin E (IgE) Signup and view all the answers

What type of immune mechanisms resist or evade specific immune effector functions?

Virulence mechanisms employed by pathogens Signup and view all the answers

What is pyroptosis in the context of HIV infection?

A highly inflammatory form of programmed cell death. Signup and view all the answers

Which of the following statements correctly describes the innate immune response to abortive infection in CD4 T cells?

It results from sensing DNA fragments produced during reverse transcription. Signup and view all the answers

What role do oral bacteria play in immune function?

They can impair B and T cell function. Signup and view all the answers

How do periodontopathogens interact with the immune system?

They trigger the release of mediators that inhibit lymphocyte function. Signup and view all the answers

What task is NOT associated with the immune response?

Igniting inflammation for non-dangerous stimuli. Signup and view all the answers

Which bacteria produce specific toxins that kill monocytes?

A.actinomycetemcomitans Signup and view all the answers

What are the components that provoke cytokine induction from Gram-negative bacteria?

Lipopolysaccharides (LPS) Signup and view all the answers

What effect do prostaglandins released by certain bacteria have on immune function?

They inhibit lymphocyte function. Signup and view all the answers

What describes the symptoms of Tuberculoid leprosy?

A few flat lesions, some large and numb Signup and view all the answers

Which of the following is a possible disease response for Mid-borderline leprosy?

It may persist, regress, or progress to other forms. Signup and view all the answers

What is a distinguishing feature of Lepromatous leprosy?

Presence of bacteria and severe nerve involvement Signup and view all the answers

Borderline tuberculoid leprosy can result in which of the following disease responses?

Can persist, revert to tuberculoid, or advance Signup and view all the answers

What characterizes the lesions found in Mid-borderline leprosy?

Lesions include reddish plaques with moderate numbness Signup and view all the answers

What type of leprosy is characterized by many lesions and does not regress?

Lepromatous leprosy Signup and view all the answers

How does the disease response differ for Tuberculoid and Lepromatous leprosy?

Tuberculoid may heal on its own; Lepromatous does not Signup and view all the answers

Which statement about Borderline lepromatous leprosy is true?

It presents many lesions, including nodules and flat lesions. Signup and view all the answers

What symptom is most likely associated with a more severe form of leprosy?

Severe nerve involvement and limb weakness Signup and view all the answers

What condition involves lesions that may progress to another form but can also revert to tuberculoid?

Borderline tuberculoid leprosy Signup and view all the answers

Study Notes

Immunity in Defense and Disease

Immunological defenses are crucial in combating microbes and tumors, as well as for reactions against transplants and diseases stemming from abnormal immune responses.
Animations on the human immune system can supplement understanding of the immune response.

Immunological Defenses Against Microbes

Pathogenic microbes interact with the human host in various ways, leading to various responses.
Anti-bacterial, anti-viral, anti-fungal, and anti-parasite immune responses are key components of defending against various infectious agents.
Understanding immune evasion mechanisms is vital.

Pathogenic Microbes

Microbiologists study four main types of microbial infectious agents: bacteria, fungi, viruses, and parasites (including helminthes and protozoa).
Understanding why pathogenic microbes are feared is vital for studying immunity.

Acute Infectious Diseases

Infectious diseases and epidemics are caused by pathogenic microbes.
The characteristics of an acute infectious disease include the type of infectious agent, the target organ, the localization (intracellular/extracellular), and the evoked immune response.
Understanding how the immune system reacts to different pathogens is important.

Innate vs Acquired Immunity to Different Pathogens

The immune system's response to distinct pathogens varies.
Responses to the same pathogen may differ.

Host-Pathogen Interaction

Host-parasite interactions differ among individuals based on the characteristics of the host and the microbe.
There is a trade-off between over- and under-reactivity (in the immune response) – an important concept that demonstrates the careful balance needed for a healthy immune response.
Hosts and parasites are locked in an adaptive race.

Location of Infectious Agents in Host Tissue

Infectious agents can be found intracellularly or extracellularly depending on their type.
This difference determines the mechanisms of immune response.

Anti-Bacterial Immunity

Innate immunity includes complement activation, phagocytosis, and inflammatory responses.
Adaptive immunity involves humoral mechanisms (antibodies—Th2 response) and cell-mediated mechanisms (Th1 response).
The immune response to extracellular bacteria is different from the response to intracellular bacteria.

Immune Response to Intracellular Bacteria

Innate immunity to intracellular bacteria is primarily from natural killer (NK) cells, which kill infected cells and secrete IFN-γ.
Acquired immunity to this type of infection (intracellular) is mainly from cell-mediated immunity (CMI) and Th1 responses.
Both activation of macrophages and lysis of infected cells by cytotoxic cells (CTLs) are crucial in the immune response to intracellular bacteria.

Feedback of Adaptive on Innate Immunity

The output on innate immunity from adaptive immunity involves different cytokines (IFN-γ, TNF; Th1 and Th2 cytokines)
The effect this interaction has on the outcome of some bacterial infections, such as Leishmaniasis, and Tuberculosis are covered.

Th1/2 Choice in Leprosy

A specific example of Th1/2 choice is shown in clinical cases of Leprosy.
Different outcomes can result from different choices in immune response, including the development of tuberculoid and lepromatous leprosy.
Outcomes of these conditions can have a significant impact (and influence) on the patient and the progression of the disease.

Anti-Viral Immunity

Humoral immunity involves neutralizing viruses and destroying virus particles by aggregation and opsonization, complement-mediated lysis.
Cell-mediated immunity (CMI) uses cytotoxic T-cells (CTLs), NK cells, and activated macrophages, directly killing infected cells.
Cytokines (interferons - IFNs) play a significant role in antiviral activity, acting early in viral diseases to inhibit intracellular replication and activate NK cells.

Immunity to Viruses

Understanding how the innate and adaptive immune systems work together to fight viral infections is essential for studying immunity.

Hepatitis B Virus (HBV) Infection

HBV infections in the liver are protracted, suggesting a tolerogenic effect on immune responses.
The liver is made up of hepatocytes, endothelium, macrophages, and lymphocytes.
The liver, however, is not the only tissue site where responses are noted
The principal cells involved in HBV infections include NK cells, T cells, B cells, and Kupffer cells.

Immunopathology Due to Viral Infections

The involvement of chemokines and their receptors in infection is mentioned
Cytokine levels and antiviral responses are discussed
Phagocytosis of viral proteins by macrophages play a key role.

Anti-Fungal Immunity

Innate immunity is mediated by phagocytic cells (neutrophils and macrophages).
Cell-mediated immunity (CMI) plays a significant role in clearing intracellular fungi; Th1 responses are crucial.

Immunity to Parasites

Immunity against intracellular protozoa is largely mediated by Th1-triggered macrophages, and immunity to helminthic infections by Th2 cells, IgE, and mast cells/basophils.
Chronic parasite infections are common due to weak innate immunity and parasitic evasive mechanisms.

Pathogens and Effective Immune Response

The table details various specific pathogens, their location (intra/extracellular), antigen recognition(MHC class I/II), and the effector actions.
This table was created based on immune interactions.

Important Issues in Immunity

The relationship between immune deficiencies and the type of microbes is an important concept.
The ways various microbes evade the immune system are examined in specific examples.
The effects of microbes on disposition, autoimmune diseases, and other illnesses are touched upon.

Microbial Evasion of Immune Responses

Microbes can avoid innate immune responses through mechanisms like resisting phagocytosis, reactive oxygen intermediates, complement activation, or anti-microbial peptide resistance.
The specific immune response can also be circumvented.

Immune Evasion Targeting Cytokine Production

Microorganisms can induce cytokine synthesis by host cells.
Significant quantities of pro-inflammatory cytokines (IL-1, IL-6, IL-8, TNF) are essential mediators in inflammatory diseases that range from arthritis to periodontal ailments.
Viral infections can affect interferon responses.

Tuberculosis (TB)

The tuberculosis bacterium uses various sophisticated methods to evade immune system responses, including mechanisms to evade cell entry, phagocytosis.
A very important point to make here is the high lipid concentration in the TB cell wall.
Pathogenesis of TB is discussed

Immune Evasion via Microbial Antigens and Variants

Various mechanisms that pathogens use to evade the immune system were presented.
Key concepts include antigenic shifting or drifting in response to selective pressures.
Viral and bacterial examples were included to aid in understanding the immune response.

HIV and Infection

A discussion of how HIV infects cells is presented followed by discussion of other immune responses.

Tasks of the Immune Response

The roles of the immune response, including differentiation between self and non-self, and the determination of what is dangerous and safe, is discussed from a complex perspective

Role of Immune Compartments, Signals, and Cytokines

Various immune mechanisms are employed to target the pathogens
How the adaptive and innate compartments and the roles of cytokines play are important concepts to grasp.

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Description

Explore the immune system's vital role in combating pathogens and tumors. This quiz covers immunological responses to various microbes, including bacteria, viruses, fungi, and parasites. Understand how the human body defends itself and how microbes evade these defenses.