lactate – waste product produced when sugar is turned into energy by the body.

lactic acidosis – dangerous build up of lactate in the blood.

late breaker – in research, this is a study presented at a medical meeting that was submitted to the conference organisers after the main programme had been decided. There are usually only a few dozen late-breakers, where the last minute results are thought important enough to include – like ‘late-breaking news’. Although this studies often contain the most exciting news, they are given much less time to present their results – maybe less than 10 minutes compared to a normal 15 or 20 minute session. These summary results are also difficult to verify because they include fewer slides and fewer details.

latent – not active at present, resting. Latently infected CD4 cells are CD4 cells that are infected with HIV but which are resting. HIV drugs do not work on resting cells.

lesion – damage to a part of the body.

life cyle – the steps for an organism to reproduce or replicate.

The HIV life cycle includes:

  • Attachment and binding to a CD4 cell).
  • Fusion or joining the cell.
  • Reverse transcription. When the single strand RNA becomes a double strand DNA.
  • Integration. When the new double-strand virus enter the CD4 cell nucleus and is integrated into humn DNA.
  • Replication. When new viral material is produced from the nucleus.
  • Assembly and maturation. When new viral mateiral is cut up and reassembed to become new active virus.
  • Budding. When the new virus leaves the CD4 cell.

See: HIV life cycle – how different drugs work in different ways.

lipid – medical term for fat. The term ‘blood lipids’ refers to cholesterol and triglyceride levels in blood.

lipoatrophy – fat loss in your arms, legs or face. Lipoatrophy is a type of lipodystrophy.

lipodystrophy – body fat changes, including fat loss (from arms, legs, buttocks and face) and/or fat gain (in abdomen, breasts and shoulders). The lipodystrophy syndrome also includes metabolic changes in lipid and glucose metabolism.

log value – a number expressed as a factor of 10 – ie 2 logs = 10 x 10=100; 3 logs = 10 x 10 x 10=1000. This measurement is used when needing to include very large and very small numbers on the same scale. A reduction by one log is a 90% reduction. A reduction by two logs is a 99% reduction etc.

Log conversion table.

long-term non-progressor (LTNP) – An HIV positive person whose CD4 count stays above 500 copies/mm3 with very low viral load for more than five years, without using ART.

Some LTNPs have kept their CD4 count above 500 for more than 10-15 years without ART. Recent guidelines suggest the LTNPs should still strongly consider using ART. This is because ongoing HIV replication is still likely to increase the risk of serious illnesses, even at low viral load levels,

Because CD4 counts gradually fall in LTNPs, just very slowly, a more accurate term is long-term slow-progressors (LTSPs).

Elite controllers (ECs) are a sub-group of LTSP who also maintain undetectable viral load (less than 50 copies/mL) without ART. See: elite controller.

low level resistance – when there is some resistance but it does not have any significant impact on how well a drug works.  The HIV drug is still sensitve and is  considered active.

LTNP / LTSP – See: long-term non-progressor.

lumbar puncture – taking a sample of spinal fluid by inserting a needle into the body at the base of the spine. Also called a spinal tap.

lymph node – small bodies in the lymphatic system, particularly at the neck, armpit, and groin, that filter bacteria and foreign particles. During infection, lymph nodes may become swollen with white blood cells (lymphocytes) fighting the infection.

lymph (or lymphatic) system – vessels, nodes, organs and clear fluid, that are part of the immune system.

lymphocyte – medical term for a white (clear) immune cell in blood, lymph or lymph tissue. Two main types of lymphocyte are B cells and T cells. CD4 cells and CD8 cells are both types of T cells. Sometimes a CD4 count is referred to as a CD4 T cell count or a T cell count.

lymphoma – name for a cancer in the lymphatic system.

Cancer: lymphoma and sarcoma