2. defence against reproductive pathogens WS

Question 1

what is a commensal organism

Answer 1

a type of microorganism that lives on or within a host organism without causing harm. In a commensal relationship, the microorganism benefits by obtaining nutrients or a place to live, while the host remains unaffected and unharmed

Question 2

what is an opportunistic pathogen

Answer 2

a microorganism that typically does not cause disease in a healthy host but can become pathogenic under certain conditions.

Question 3

what is a pathogenic micro-organism

Answer 3

a type of microorganism, such as bacteria, viruses, fungi, or parasites, that can cause disease in a host organism. Unlike commensal organisms, pathogenic microorganisms have the inherent ability to invade the host’s tissues, evade the immune system, and produce toxins or other harmful substances that lead to illness

Question 4

which parts of the female reproductive tract are considered sterile. why? when would this not be the case

Answer 4

Question 5

what is pyometra

Answer 5

uterine infection characterized by the accumulation of pus within the uterus.
- Pyometra typically develops due to hormonal changes in the reproductive cycle, especially following estrus (heat). Elevated levels of the hormone progesterone after ovulation cause the uterine lining to thicken and glands to secrete, creating an environment conducive to bacterial growth.
- Bacteria, most commonly Escherichia coli (E. coli) originating from the normal flora of the lower reproductive tract or gastrointestinal tract, can enter and infect the uterus during this susceptible period.

2 types:
- open: cervix remains slightly open
- closed: cervix is closed trapping pus inside the uterus

Question 6

what is metritis

Answer 6

inflammation of the uterine wall, often occurring after partuition or abortion. The condition usually arises when bacteria invade the uterus, particularly when there has been some trauma or other compromising factor during the birthing process.

Question 7

what is endometritis

Answer 7

Endometritis is an inflammation of the inner lining of the uterus, known as the endometrium. It is typically less severe than metritis but still significant, particularly because it can affect fertility and overall reproductive health.

Question 8

what is the “typical” origin of the micro-organism found in the female reproductive tract and how do they get there (mare, bitch, cow)

Answer 8

Question 9

what could make bacterial contamination of the uterus more likely to occur

Answer 9

• partuition
• oestrus
• breeding (AI or mating)
• previous conditions
• immuno compromise

Question 10

what features of the bacteria that influence the female reproductive tract influence their potential invasiveness and pathogenicity

Answer 10

• variation in the bacterial surface proteins change adhesive and invasive properties
• potential synergism between bacterial species (if both A. pyogenes and E.coli are present simultaneously the overall pathogenicity is increased)

Question 11

what features contribute to resistance to infection of female reproductive pathogens

Answer 11

• physical drainage via vagina and vulva
• epithelial barrier
• local mucosal glycosaminoglycan and IgA production
• Anti-microbial peptides e.g. defensin

Question 12

which immune cells are present in the reproductive tract and are involved in the host response against infection

Answer 12

• monocytes
• neutrophils
• macrophages
• NK cells
• T cells
• B cells

Question 13

Inflammation can cause abortion, what host receptors are involved in recognising pathogens and what do they recognise:

Answer 13

• Host cells express pattern recognition receptors (Toll-like receptor) that recognise highly conserved structures found in prokaryotes called pathogen-associated molecular patterns (PAMPs).
• This recognition will stimulate innate immune responses
• The Toll-like Rs are regulated by sex steroids hence the endocrine system can control localised immune defences in the female tract.

Question 14

In general terms, how does oestradiol and progesterone affect immunity? Thus, how might immune function changed across the oestrous cycle.

Answer 14

Oestradiol:
- Oestradiol tends to enhance immune responses
- Increases the activity of immune cells such as macrophages and neutrophils
- promotes the production of inflammatory cytokines and chemokines
- helps the reproductive tract defend against infections, particularly during the time when sperm are introduced.
- upregulates the expression of Toll-like receptors (TLRs) on immune cells, which are crucial for recognizing pathogens.
- contributes to maintaining the epithelial barrier and increasing the production of antimicrobial peptides, further boosting local immunity.

Progesterone:
- Progesterone has an immunosuppressive effect, which is crucial for creating a more tolerant environment in the reproductive tract
- This suppression is necessary to protect the semi-allogeneic fetus (which is genetically different from the mother) from being attacked by the maternal immune system.
- reduces the activity of immune cells like macrophages and neutrophils and lowers the production of inflammatory cytokines.
- Progesterone downregulates the expression of Toll-like receptors (TLRs) and other molecules involved in the immune response, reducing the likelihood of an inflammatory response that could harm a developing embryo or fetus.

Question 15

Describe how the presence of sperm in the female tract constitutes an immunological challenge and what processes may help the sperm (and female) survive.

Answer 15

• carry foreign antigens

Processes That Help Sperm and Female Survival:
- Seminal fluid contains immunosuppressive factors that help modulate the female immune response to sperm. These factors can reduce the activity of immune cells and cytokine production in the female reproductive tract, helping to prevent an excessive immune reaction against the sperm.
- Cervical mucus acts as a selective barrier. During ovulation, the consistency of cervical mucus changes, becoming more receptive to sperm passage. This mucus helps protect sperm from immune cells and antibodies in the female tract by providing a more supportive environment for their journey to the uterus.
- Hormonal Modulation
- The epithelial cells lining the female reproductive tract produce mucosal secretions and antimicrobial peptides that help protect against infections without severely compromising sperm survival. These secretions include substances like defensins that can neutralize pathogens while sparing sperm.
- The female reproductive tract has mechanisms to regulate inflammation in response to sperm. For example, after the introduction of sperm, there may be a controlled, localized immune response that clears potential pathogens without significantly harming the sperm.
- The female immune system can develop tolerance to sperm through repeated exposure during intercourse, which reduces the likelihood of an immune response with each subsequent exposure.

Question 16

The fetusis described as beingsemi-allogeneic. What does this mean?

Answer 16

refers to the fetus’s relationship to the mother’s immune system. In immunology, “allogeneic” means originating from the same species but genetically different, such as between individuals of the same species who are not genetically identical.

The fetus is considered semi-allogeneic because it inherits half of its genetic material from the mother and half from the father. Although the mother and fetus share some genetic material (from the mother’s side), the paternal genes are foreign to the mother’s immune system. This makes the fetus partially allogeneic from the mother’s perspective.

The “semi” part of the term highlights that while the fetus is not fully allogeneic (like a transplant from a completely unrelated individual might be), it is still partially so due to the paternal genes. Despite this semi-allogeneic nature, the mother’s immune system typically does not reject the fetus because of complex immunological mechanisms that help protect the fetus and facilitate a successful pregnancy.