Immunocontraception

Key takeaways

Immunocontraception belongs to science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Immunocontraception to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Immunocontraception from memory before moving on to harder problems.

Reference excerpt

Immunocontraception is the use of an animal's immune system to prevent it from fertilizing offspring. Contraceptives of this type are not currently approved for human use. Typically immunocontraception involves the administration of a vaccine that induces an adaptive immune response which causes an animal to become temporarily infertile. Contraceptive vaccines have been used in numerous settings for the control of wildlife populations. However, experts in the field believe that major innovations are required before immunocontraception can become a practical form of contraception for human beings. Thus far immunocontraception has focused on mammals exclusively. There are several targets in mammalian sexual reproduction for immune inhibition. They can be organized into three categories.

Gamete production Organisms that undergo sexual reproduction must first produce gametes, cells which have half the typical number of chromosomes of the species. Current approaches to immunity that prevents gamete production also inhibits sex hormone production and so has effects similar to castration such as prevention of secondary sexual characteristics development. Gamete function After gametes are produced in sexual reproduction, two gametes must combine during fertilization to form a zygote, which again has the full typical number of chromosomes of the species. Methods that target gamete function prevent this fertilization from occurring and are true contraceptives. Gamete outcome Shortly after fertilization a zygote develops into a multicellular embryo that in turn develops into a larger organism. In placental mammals this process of gestation occurs inside the reproductive system of the mother of the embryo. Immunity that targets gamete outcome induces abortion of an embryo while it is within its mother's reproductive system.

Medical use Immunocontraception is not currently available but is under study.

Obstacles

Variability of immunogenicity In order for an immunocontraceptive to be palatable for human use, it would need to meet or exceed the efficacy rates of currently popular forms of contraception. Currently the maximum reduction of fertility due to sperm vaccines in laboratory experiments with mice is ~75%. The lack of efficacy is due to variability of immunogenicity from one animal to another. Even when exposed to the exact same vaccine, some animals will produce abundant antibody titers to the vaccine's antigen, while others produce relatively low antibody titers. In the Eppin trial that attained 100% infertility, a small sample size (only 9 monkeys) was used, and even among this small sample 2 monkeys were dropped from the study because they failed to produce sufficiently high antibody titers. This trend—high efficacy when antibody titers are above a threshold coupled with variability in how many animals reach such a threshold—is seen throughout immunocontraception and immune-based birth control research. A long-term study of PZP vaccination in deer that spanned 6 years found that infertility was directly related to antibody titers to PZP. The phase II clinical trial of hCG vaccines was quite successful among women who had antibody titers above 50 ng/mL, but quite poor among those with antibody titers below this threshold.

Lack of mucosal immunity Mucosal immunity, which includes immune function in the female reproductive tract, is not as well understood as humoral immunity. This may be an issue for certain contraceptive vaccines. For instance, in the second LDH-C4 primate trial that had negative results, all of the immunized macaque monkeys developed high antibody titers against LDH-C4 in serum, but antibodies against LDH-C4 were not found in the monkeys' vaginal fluids. If antibodies against LDH-C4 do indeed inhibit fertilization, then this result highlights how the difference in the functioning of mucosal immunity from humoral immunity may be critical to the efficacy of contraceptive vaccines.

Adverse effects Whenever an immune response is provoked, there is some risk of autoimmunity. Therefore, immunocontraception trials typically check for signs of autoimmune disease. One concern with zona pellucida vaccination, in particular, is that in certain cases it appears to be correlated with ovarian pathogenesis. However, ovarian disease has not been observed in every trial of zona pellucida vaccination, and when observed, has not always been irreversible.

Gamete production

Gonadotropin-releasing hormone The production of gametes is induced in both male and female mammals by the same two hormones: follicle-stimulating hormone (FSH) and luteinizing hormone (LH). The production of these in turn is induced by a single releasing hormone, gonadotropin-releasing hormone (GnRH), which has been the focus of most of the research into immunocontraception against gamete production. GnRH is secreted by the hypothalamus in pulses and travels to the anterior pituitary gland through a portal venous system. There it stimulates the production of FSH and LH. FSH and LH travel through the general circulatory system and stimulate the functioning of the gonads, including the production of gametes and the secretion of sex steroid hormones. Immunity against GnRH thus lessens FSH and LH production which in turn attenuates gamete production and secondary sexual characteristics. While GnRH immunity has been known to have contraceptive effects for some time, only in the 2000s has it been used to develop several commercial vaccines. Equity® Oestrus Control is a GnRH vaccine marketed for use in non-breeding domestic horses. Repro-Bloc is GnRH vaccine marketed for use in domestic animals in general. Improvac® is a GnRH vaccine marketed for use in pigs not as a contraceptive, but as an alternative to physical castration for the control of boar taint. Unlike the other products which are marketed for use in domestic animals, GonaCon™ is a GnRH vaccine being developed as a United States Department of Agriculture initiative for use for control of wildlife, specifically deer. GonaCon has also been used on a trial basis to control kangaroos in Australia.

… excerpt ends here. Continue reading the full article.

Worked examples

Example 1 — a first encounter with Immunocontraception

Start with the simplest possible case. Write down what Immunocontraception claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Immunocontraception before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Immunocontraception ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Immunocontraception

In research: Immunocontraception appears in science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Immunocontraception in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Immunocontraception is common in secondary-school and first-year university syllabi. It links to neighbouring topics Experimental methods of birth control, Immune system, Theriogenology, so understanding it makes those chapters shorter.
In everyday life: Look for Immunocontraception outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

How to study Immunocontraception in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Immunocontraception means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Immunocontraception out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Immunocontraception in simple terms?

Immunocontraception is the use of an animal's immune system to prevent it from fertilizing offspring. Contraceptives of this type are not currently approved for human use.

Why does Immunocontraception matter?

Because it connects several science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Immunocontraception?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Immunocontraception.