What causes infection in a dogs lymph node?

I took my dog to the vet (his neck is swollen) the vet put him on Tribrissen for a week. I forgot to ask the vet what causes infection in a dogs Lymph Node?? any information would be helpful, Thanks

Lymph nodes are the "clearing house" for any infections so by the neck a tooth, nasty mouth, infected ear or lymphosarcoma are all possibilites.

My dog had this when he was a puppy. The vet said it was from a puncture wound. The only puncture wound he had was his 3rd DAPP given by the breeder. After talking to the breeder, she told me that she had read in some AKC literature that the lymph node infection could have been caused by his vaccinations 4 days prior.

Lymph nodes are a part of the immune system that fights infections in the body, the presence of infection often causes lymph nodes to increase in size.The lymph nodes make antibodies that will help keep you from being infected with a particular germ in the future. All kinds of infections can cause node enlargement - strep, bacteria, a virus, ear and fungal infection etc.There are different types of infections in the lymph glands such as:Reactive hyperplasia - the most common.Primary or secondary inflammation of the node (lymphadenitis)Mineral-associated lymphadenopathy metastatic neoplasia like lymphomaLymph node haemorrhage, infarction or oedema.Hopefully you have the reactive type - the rest are pretty nasty.