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Antisperm antibodies 

The testes are designed to keep the sperm ‘safe’ and protected from the immune system however when this space is breached, for example by an injury, the immune system can develop antibodies against its own sperm. They are known as antisperm antibodies (ASAs). ASAs can either circulate in the blood or bind to the sperm. The impact on the sperm depends on where the antibodies bind to on the sperm.  


In most cases, ASAs are not clinically significant. There are a range of ASAs with different effects and most do not have a negative impact on fertility. In some cases though, ASAs can impact fertility by decreasing sperm concentration, motility and the ability for sperm to penetrate through cervical mucous to get to the egg. Fertilisation can also be impacted if ASAs are attached to the head of the sperm.  


Causes of ASAs

  • Injury or trauma

  • Genital duct infection or obstruction

  • Surgery (including vasectomy)

  • Idiopathic (unknown cause)



In a routine semen analysis, ASAs are suspected when sperm with poor motility clumps together. This can indicate the need for an ASA test  


Testing for ASAs  

Direct mixed antiglobulin reaction (MAR) detects antibodies bound to sperm cells. Routinely performed in some labs by mixing fresh sperm with latex particles coated with a type of human antibody. The coated particles will attached to the sperm wherever ASA are located.  


Indirect MAR – detects antibodies in serum or semen plasma. This is more complicated and takes more time but is more efficient.  


The main issue with these tests is that there is a lack of method standardisation and inconsistent cut-off values.  


Management of ASA’s

  • Lab sperm washing techniques can improve motility issues

  • Corticosteroid therapy (studies had shown mixed results on this): weakens immunity to reduce antibodies

  • ICSI – preferred treatment: the impact of ASAs becomes irrelevant as the sperm is injected directly into the egg. 

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